WO2015130106A1 - Lithium-nickel based cathode active material, method for preparing same, and lithium secondary battery including same - Google Patents

Lithium-nickel based cathode active material, method for preparing same, and lithium secondary battery including same Download PDF

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WO2015130106A1
WO2015130106A1 PCT/KR2015/001882 KR2015001882W WO2015130106A1 WO 2015130106 A1 WO2015130106 A1 WO 2015130106A1 KR 2015001882 W KR2015001882 W KR 2015001882W WO 2015130106 A1 WO2015130106 A1 WO 2015130106A1
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active material
positive electrode
lithium
electrode active
nickel
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PCT/KR2015/001882
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French (fr)
Korean (ko)
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임진형
신호석
이동훈
오현진
진주홍
정왕모
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주식회사 엘지화학
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Priority to PL15755793T priority Critical patent/PL3113262T3/en
Priority to EP15755793.5A priority patent/EP3113262B1/en
Priority to BR112016017104A priority patent/BR112016017104B8/en
Priority to CN201580006499.XA priority patent/CN105940535B/en
Priority to EP18197087.2A priority patent/EP3439085A1/en
Priority to US15/037,003 priority patent/US10608251B2/en
Priority to JP2016564935A priority patent/JP6515116B2/en
Publication of WO2015130106A1 publication Critical patent/WO2015130106A1/en

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    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
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    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
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    • H01M4/362—Composites
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    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/502—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese for non-aqueous cells
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    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
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    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/523—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron for non-aqueous cells
    • H—ELECTRICITY
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    • H01M4/00—Electrodes
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    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
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    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
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    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the present invention provides a positive electrode active material including a lithium-nickel-based transition metal composite oxide doped with alkaline earth metal having +2 oxidized water and a phosphate coating layer formed on the surface of the composite oxide, which reduces lithium by-products and improves structural stability.
  • the present invention relates to a positive electrode including the same and a secondary battery including the positive electrode.
  • lithium secondary batteries having high energy density and voltage, long cycle life, and low self discharge rate have been commercially used.
  • lithium secondary battery In order to use a lithium secondary battery in a battery vehicle, it has to exhibit high energy density and a large output in a short time, and to be used for more than 10 years under severe conditions, so it has superior safety and safety than a conventional small lithium secondary battery. Long lifespan characteristics are inevitably required.
  • the lithium secondary battery includes a positive electrode including a positive electrode active material capable of occluding and releasing lithium ions, a negative electrode including a negative electrode active material capable of occluding and releasing lithium ions, and an electrode assembly having a microporous separator interposed between the positive electrode and the negative electrode. It means a battery containing a non-aqueous electrolyte containing lithium ions.
  • Examples of the positive electrode active material of a lithium secondary battery include transition metal oxides such as lithium cobalt oxide (LiCoO 2 ), lithium-manganese oxide (LiMn 2 O 4 ), or lithium-nickel oxide (LiNiO 2 ), and some of these transition metals are different. Composite oxides substituted with transition metals are used.
  • transition metal oxides such as lithium cobalt oxide (LiCoO 2 ), lithium-manganese oxide (LiMn 2 O 4 ), or lithium-nickel oxide (LiNiO 2 ), and some of these transition metals are different.
  • Composite oxides substituted with transition metals are used.
  • LiCoO 2 is widely used because of its excellent physical properties such as excellent cycle characteristics, but it is low in safety and expensive due to resource limitations of cobalt as a raw material, and is not suitable for mass use as a power source in fields such as electric vehicles. There is.
  • Lithium-manganese oxides such as LiMnO 2 or LiMn 2 O 4 have the advantage of using abundant resources and environmentally friendly manganese as raw materials, attracting much attention as a cathode active material that can replace LiCoO 2 , but Lithium-manganese oxides have disadvantages of low capacity and poor cycle characteristics.
  • lithium-nickel-based oxides such as LiNiO 2 have a lower discharge cost than the cobalt-based oxides and have a high discharge capacity when charged at 4.3 V.
  • the reversible capacity of the doped LiNiO 2 is about the capacity of LiCoO 2 (about 165 mAh / g) in excess of about 200 mAh / g).
  • lithium-nickel oxides have the advantage of high capacity, but due to the volume change accompanying the charge / discharge cycle, there is a sudden phase transition of the crystal structure, resulting in voids in the cracks or grain boundaries of the particles, and during storage or cycle When excessive gas is generated and exposed to air and moisture, there is a problem that the chemical resistance is sharply lowered on the surface, and thus the practical use is limited.
  • lithium transition metal oxides in which a part of nickel is substituted with other transition metals such as manganese and cobalt have been proposed.
  • these metal-substituted nickel-based lithium transition metal oxides have advantages in that they have relatively superior cycle characteristics and capacity characteristics, but even in this case, the cycle characteristics deteriorate rapidly during long-term use, and swelling by gas generation in a battery, Problems such as low chemical stability have not been sufficiently solved. Therefore, it is necessary to develop a technology capable of solving the high temperature safety problem while using a lithium nickel-based positive electrode active material suitable for high capacity.
  • the lithium-nickel positive electrode active material has a high generation of lithium by-products (Li 2 CO 3 and LiOH) on the surface, and these lithium by-products form a resistive film and react with a solvent (for example, PVDF) to prepare a cathode active material slurry to gel. Not only does it cause gas, but also generates swelling in the battery, which has the disadvantage of greatly reducing the battery life characteristics.
  • a solvent for example, PVDF
  • the inventors of the present invention are studying a method of improving the structural stability and reducing lithium by-products, thereby suppressing the swelling and resistive film formation caused by the by-products, thereby improving battery life characteristics.
  • Lithium by-products on the surface of the positive electrode active material prepared by doping an alkaline earth metal having a +2 valence oxidation number to a transition metal composite oxide and forming a phosphate coating layer on the surface of the composite oxide, and at the same time, life characteristics of a battery including the same
  • the present invention was completed by confirming this increase.
  • An object of the present invention is to provide a cathode active material including a lithium-nickel transition metal composite oxide and a coating layer of phosphorous oxide formed on the surface of the composite oxide, with reduced lithium by-products and improved structural stability.
  • Another object of the present invention is to provide a method for producing the cathode active material.
  • Still another object of the present invention is to provide a cathode for a secondary battery, in which a cathode active material slurry including the cathode active material is coated on a current collector.
  • another object of the present invention is to provide a secondary battery having excellent lifespan characteristics, including a separator and an electrolyte interposed between the positive electrode, the negative electrode, the positive electrode and the negative electrode for the secondary battery.
  • the present invention is a lithium-nickel transition metal composite oxide having a layered structure represented by the formula (1); And it provides a cathode active material comprising a coating layer consisting of a phosphate oxide formed on the complex oxide surface.
  • M is at least one element selected from the group consisting of Mn, Co, Cr, Fe, V and Zr,
  • A is at least one alkaline earth metal with +2 oxidation number
  • D is at least one element selected from the group consisting of S, N, F, Cl, Br, I and P.
  • the present invention is to prepare a lithium-nickel-based transition metal complex oxide represented by the formula (1) by mixing and sintering the alkaline earth metal precursor having a +2 valence oxidation number in the mixed solution of the transition metal precursor and the lithium precursor (step 1 ); And mixing and sintering a phosphate precursor to the complex oxide to form a phosphate coating layer on the outer surface of the complex oxide (step 2).
  • the present invention provides a secondary battery positive electrode, the positive electrode active material slurry containing the positive electrode active material is coated on the current collector.
  • the present invention provides a lithium secondary battery comprising a separator and an electrolyte interposed between the positive electrode and the negative electrode for the secondary battery, the positive electrode and the negative electrode.
  • the positive electrode active material according to the present invention includes a lithium-nickel-based transition metal composite oxide doped with an alkaline earth metal having +2 oxidation number and a phosphate coating layer formed on the outer surface of the composite oxide, thereby providing an alkaline earth metal having +2 oxidation number (The cation thereof) is located in a lithium site (lithium cation site) in the complex oxide or in some empty space in the crystal lattice to act as a kind of pillar in the crystal lattice to promote structural stability of the positive electrode active material, and By reducing the natural loss of the cation can reduce the production of lithium by-products (LiOH and Li 2 CO 3 ) generated by the natural loss of the lithium cation, and at the same time the phosphate coating layer surrounding the outer surface of the composite oxide By reacting with lithium by-products present on the outer surface to reduce lithium by-products, lithium By-products can be significantly reduced to suppress swelling resulting from the lithium by-products and to prevent resist film formation.
  • the secondary battery including the cathode active material according to the present invention may have excellent capacity characteristics and structural stability during charging and discharging, and swelling may be suppressed to exhibit excellent life characteristics.
  • the present invention can be easily applied to an industry requiring the high capacity and long lifespan of an electric vehicle.
  • FIG. 1 is a graph showing a result of comparing life characteristics of a battery according to an exemplary embodiment of the present invention.
  • the present invention provides a positive electrode active material in which a lithium-nickel transition metal composite oxide is doped with an alkaline earth metal having a + 2-valent oxidation number, and a phosphate coating layer is formed on the outer surface of the composite oxide to reduce lithium by-products and improve structural stability. To provide.
  • the cathode active material according to an embodiment of the present invention is a lithium-nickel-based transition metal composite oxide having a layered structure represented by Formula 1 below; And a phosphate coating layer formed on the outer surface of the composite oxide.
  • the cathode active material is based on lithium-nickel oxide (LiNiO 2 ), and can supplement structural instability by adding an element represented by M in Chemical Formula 1, and structural doping by doping an element represented by A At the same time, the natural loss of lithium cations can be suppressed, thereby reducing the amount of lithium by-products generated.
  • the electrochemical properties may vary greatly according to the molar ratio of the elements represented by nickel (Ni) and M and A. Therefore, it may be important to properly adjust the molar ratio of the elements represented by nickel (Ni) and M and A.
  • the content of the nickel (Ni) in the positive electrode active material may be 70 mol% or more based on the total amount of metal components excluding lithium, that is, the total amount of elements represented by Ni, M, and A in Formula 1, and Preferably at least 75 mol%.
  • the element represented by M may be one or two or more of the aforementioned elements, preferably, M may be Mn b1 Co b2 , where 0 ⁇ b1 + b2 ⁇ 0.5, preferably 0 ⁇ b1 + b2 ⁇ 0.3.
  • the battery may be discharged and capacity characteristics of the secondary battery including the positive electrode active material. Properties may be excellent.
  • the element represented by A is doped in a lithium site (lithium cation site) in order to prevent mixing of the nickel cation in the lithium layer in the positive electrode active material, wherein A is an alkaline earth metal having +2 oxidation number and the nickel cation There is a characteristic of having a larger ion radius.
  • the alkaline earth metal having a +2 oxidation number represented by A may be located in a lithium site (lithium cation site) or an empty space in a crystal lattice in the crystal structure of the cathode active material, thereby achieving charge balance. It is possible to suppress cation mixing in which nickel cations are incorporated into lithium cation sites, and act as a kind of filler in the crystal lattice to promote structural stability of the cathode active material and to reduce natural loss of lithium cations. Can be.
  • the alkaline earth metal having an oxidation number of +2 represented by A in Formula 1 is Sr.
  • D is an anion having an oxidation number of -1 or -2, and oxygen ions in Chemical Formula 1 may be substituted with the anion in a predetermined range.
  • the anion may be at least one element selected from the group consisting of S, N, F, Cl, Br, I, and P.
  • the substitution of the anion may improve the bonding strength with the transition metal and the positive electrode Structural transition in the active material can be prevented, resulting in improved life characteristics of the battery.
  • the amount of substitution of the anion is too large (y ⁇ 0.2), an incomplete crystal structure may be formed, which may lower the lifespan of the battery.
  • the cathode active material includes a phosphate coating layer formed on the outer surface of the lithium-nickel-based transition metal composite oxide represented by Chemical Formula 1.
  • the phosphate coating layer may have a thickness of several nanometers to several tens of nanometers or more, and specifically, the thickness may be 1 nm to 100 nm.
  • the phosphate coating layer reacts with lithium by-products present on the outer surface of the composite oxide, that is, LiOH and Li 2 CO 3 to form Li 3 PO 4 to reduce lithium by-products, thereby inhibiting swelling caused by the by-products and being resistant. It is possible to prevent the formation of the film, and by reacting with the lithium-nickel-based transition metal complex oxide represented by the formula (1) to form a reactant comprising a structure represented by the formula (2) in the transition metal layer to improve the structural stability of the positive electrode active material It can increase. Thus, the storage characteristics and lifespan characteristics of the secondary battery including the cathode active material may be improved.
  • Phosphorus precursors that are raw materials of the phosphate include (NH 4 ) 2 HPO 4 , (NH 4 ) 2 H 2 PO 4 , (NH 4 ) 3 PO 4 ⁇ 3H 2 O, H 3 PO 4 and P 2 O 5 It may be one or more selected from the group consisting of, preferably (NH 4 ) 2 HPO 4 It may be.
  • the present invention provides a method for producing the positive electrode active material to reduce the lithium by-products and improve the structural stability.
  • a lithium-nickel-based transition represented by Chemical Formula 1 is obtained by mixing and sintering an alkaline earth metal precursor having +2 valence oxidation number in a mixed solution of a transition metal precursor and a lithium precursor. Preparing a metal complex oxide (step 1); And adding a phosphate precursor to the lithium-nickel-based transition metal composite oxide and sintering it to form a phosphate coating layer on the outer surface of the composite oxide (step 2).
  • Step 1 is a step for preparing a lithium-nickel-based transition metal composite oxide doped with an alkaline earth metal represented by Chemical Formula 1, and is not particularly limited, but may be prepared by a method commonly known in the art. It may be prepared by a solid phase reaction method, coprecipitation method, sol-gel method, hydrothermal synthesis method and the like.
  • the lithium-nickel transition metal composite oxide is prepared by dissolving a nickel precursor constituting the nickel-based transition metal composite oxide and a transition metal precursor except for nickel in a solvent, followed by coprecipitation, to prepare a transition metal composite hydroxide. After preparing a mixed solution by adding a lithium precursor, it can be prepared by mixing and sintering an alkaline earth metal precursor having an oxidation number of +2.
  • the transition metal complex hydroxide may be represented by Me (OH 1-x ) 2 (0 ⁇ x ⁇ 0.5), and Me represents a transition metal and is represented by Ni a M b in Chemical Formula 1.
  • the nickel precursor, the transition metal precursor except nickel, and the alkaline earth metal precursor having a +2 valence oxidation number are used by adjusting the nickel to be 70 mol% or more with respect to the total amount of the metal components except lithium. It may be desirable.
  • the sintering in step 1 may be performed by heat treatment for 20 hours to 30 hours at a temperature of 700 °C to 900 °C, but is not limited thereto.
  • the transition metal precursor and the lithium precursor are not particularly limited, and may be in the form of a salt of each metal, for example, nitrate, sulfate, carbonate, hydroxide, acetate, and acetate. ), Oxalate, chloride, and the like.
  • the alkaline earth metal precursor having an oxidation number of +2 may be an alkaline earth metal salt, and specifically, may be SrCO 3 .
  • Step 2 is to form a phosphate coating layer on the outer surface of the lithium-nickel-based transition metal composite oxide doped with alkaline earth metal prepared in step 1, to produce a cathode active material having less lithium by-product and excellent structural stability
  • a phosphate precursor may be added to the lithium-nickel-based transition metal composite oxide and sintered.
  • the sintering in step 2 may be performed by heat treatment within 10 hours at a temperature of 100 °C to 700 °C, specifically, the heat treatment may be performed for a time within the range of 1 minute to 10 hours.
  • the phosphate precursor may be as mentioned above or included.
  • the present invention provides a positive electrode for a secondary battery in which a positive electrode slurry containing the positive electrode active material is coated on a current collector.
  • the positive electrode according to an embodiment of the present invention may be prepared by applying a positive electrode active material slurry containing the positive electrode active material to a positive electrode current collector, drying and rolling.
  • the positive electrode current collector may be generally used having a thickness of 3 ⁇ m to 500 ⁇ m, and is not particularly limited as long as it has a high conductivity without causing chemical changes in the battery, for example, stainless steel, aluminum, nickel, titanium , Surface treated with carbon, nickel, titanium or silver on the surface of calcined carbon or aluminum or stainless steel may be used.
  • the positive electrode active material slurry may be prepared by adding and mixing an additive such as a binder, a conductive material, a filler, and a dispersant to the positive electrode active material.
  • the binder is a component that assists the bonding between the positive electrode active material and the conductive material and the current collector, and may generally be added in an amount of 1 wt% to 30 wt% based on the total amount of the positive electrode active material.
  • Such binders are not particularly limited and may be conventional ones known in the art, but include, for example, vinylidene fluoride-hexafluoropropylene copolymer (PVBF-co-HEP), polyvinylidenefluoride, and polyacryl.
  • Ronitrile polyacrylonitrile
  • polymethylmethacrylate polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, poly 1 or 2 or more types selected from the group consisting of propylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene-butyrene rubber (SBR) and fluorine rubber.
  • EPDM ethylene-propylene-diene monomer
  • SBR styrene-butyrene rubber
  • the conductive material may be added at 0.05 wt% to 5 wt% based on the total weight of the positive electrode active material.
  • a conductive material is not particularly limited and is not particularly limited as long as it is conductive without causing side reactions with other elements of the battery. Examples thereof include graphite such as natural graphite and artificial graphite; Carbon blacks such as carbon black (super-p), acetylene black, ketjen black, channel black, furnace black, lamp black and summer black; Conductive fibers such as carbon fibers and metal fibers; Metal powders such as carbon fluoride powder, aluminum powder and nickel powder; Conductive whiskers such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives.
  • the filler may be used as necessary to determine whether or not to be used as a component to suppress the expansion of the positive electrode, and is not particularly limited as long as it is a fibrous material without causing chemical change in the battery, for example, olefin polymers such as polyethylene polypropylene; It may be a fibrous material such as glass fiber, carbon fiber.
  • the dispersant is not particularly limited, but may be, for example, isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or the like.
  • the coating may be performed by a method commonly known in the art, but for example, the positive electrode active material slurry may be distributed on an upper surface of one side of the positive electrode current collector, and then uniformly dispersed using a doctor blade or the like. Can be.
  • the method may be performed by a die casting method, a comma coating method, a screen printing method, or the like.
  • the drying is not particularly limited, but may be performed within one day in a vacuum oven at 50 °C to 200 °C.
  • the present invention provides a lithium secondary battery comprising a separator and an electrolyte interposed between the positive electrode and the negative electrode for the secondary battery, the positive electrode and the negative electrode.
  • a lithium-nickel transition metal composite oxide is doped with an alkaline earth metal having a +2 oxidation number, and a phosphate coating layer is formed on the surface to reduce lithium by-products and improve structural stability.
  • a separator and an electrolyte interposed between the positive electrode and the negative electrode including the improved positive electrode active material, the positive electrode and the negative electrode.
  • the lithium secondary battery has a capacity retention ratio of 90% or more at initial capacity in 55 cycles of 1.0 C charge and 1.0 C discharge conditions at 45 ° C.
  • the negative electrode is not particularly limited, but may be prepared by coating a negative electrode active material slurry containing a negative electrode active material on one side of a negative electrode current collector and then drying it.
  • the negative electrode active material slurry may include a binder, a conductive material, a filler, and a dispersant in addition to the negative electrode active material. It may include additives such as.
  • the negative electrode current collector may be the same as or included in the aforementioned positive electrode current collector.
  • the negative electrode active material is not particularly limited and may be a carbon material, lithium metal, silicon, tin, or the like in which lithium ions commonly known in the art may be occluded and released.
  • a carbon material may be used, and as the carbon material, both low crystalline carbon and high crystalline carbon may be used.
  • Low crystalline carbon includes soft carbon and hard carbon
  • high crystalline carbon includes natural graphite, kish graphite, pyrolytic carbon, liquid crystalline carbon
  • High temperature calcined carbon such as fibers (mesophase pitch based carbon fiber), meso-carbon microbeads, liquid crystal pitch (mesophase pitches) and petroleum or coal tar pitch derived cokes.
  • Additives such as binders, conductive materials, fillers, and dispersants used in the negative electrode may be the same as or included in the aforementioned positive electrode.
  • the separator may be an insulating thin film having high ion permeability and mechanical strength, and may generally have a pore diameter of 0.01 ⁇ m to 10 ⁇ m and a thickness of 5 ⁇ m to 300 ⁇ m.
  • a porous polymer film made of a polyolefin-based polymer such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, ethylene / methacrylate copolymer, etc. may be used alone. Alternatively, these may be laminated and used, or a nonwoven fabric made of a conventional porous nonwoven fabric, for example, a high melting glass fiber, polyethylene terephthalate fiber, or the like may be used, but is not limited thereto.
  • the electrolyte may include an organic solvent and a lithium salt commonly used in the electrolyte, and are not particularly limited.
  • lithium salt of the anion is F -, Cl -, I - , NO 3 -, N (CN) 2 -, BF 4 -, ClO 4 -, PF 6 -, (CF 3) 2 PF 4 -, (CF 3 ) 3 PF 3 -, (CF 3) 4 PF 2 -, (CF 3) 5 PF -, (CF 3) 6 P -, CF 3 SO 3 -, CF 3 CF 2 SO 3 -, (CF 3 SO 2 ) 2 N -, (FSO 2 ) 2 N -, CF 3 CF 2 (CF 3) 2 CO -, (CF 3 SO 2) 2 CH -, (SF 5) 3 C -, (CF 3 SO 2) 3 C -, CF 3 (CF 2 ) 7 SO 3 -, CF 3 CO 2 -, CH 3 CO 2 -, SCN - , and (CF 3 CF 2 SO 2) 2 N - be at least one selected from the group consisting of have.
  • Typical organic solvents include propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, dipropyl carbonate, dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxy ethane and vinylene carbonate.
  • Sulfolane, gamma-butyrolactone, propylene sulfite and tetrahydrofuran may be one or more selected from the group consisting of.
  • ethylene carbonate and propylene carbonate which are cyclic carbonates among the carbonate-based organic solvents, are highly viscous organic solvents, and thus may be preferably used because they dissociate lithium salts in electrolytes well.
  • a low viscosity, low dielectric constant linear carbonate such as mixed in an appropriate ratio it can be more preferably used to make an electrolyte having a high electrical conductivity.
  • the electrolyte may be pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, hexa phosphate triamide, nitrobenzene to improve the charge and discharge characteristics, flame retardancy characteristics, etc. as necessary.
  • Derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N, N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrroles, 2-methoxy ethanol, aluminum trichloride, and the like. have.
  • the solvent may further include a halogen-containing solvent such as carbon tetrachloride or ethylene trifluoride to impart nonflammability, may further include carbon dioxide gas to improve high temperature storage characteristics, and may further include fluoro-ethylene carbonate. ), Propene sultone (PRS), and fluoro-prpylene carbonate (FPC).
  • a halogen-containing solvent such as carbon tetrachloride or ethylene trifluoride to impart nonflammability
  • PRS Propene sultone
  • FPC fluoro-prpylene carbonate
  • an electrode assembly is formed by disposing a separator between a positive electrode and a negative electrode, and the electrode assembly may be manufactured by putting an electrolyte into a cylindrical battery case or a square battery case. Alternatively, after stacking the electrode assembly, it may be prepared by impregnating it in an electrolyte and sealing the resultant obtained in a battery case.
  • the battery case used in the present invention may be adopted that is commonly used in the art, there is no limitation on the appearance according to the use of the battery, for example, cylindrical, square, pouch type or coin using a can (coin) type and the like.
  • the lithium secondary battery according to the present invention may not only be used in a battery cell used as a power source for a small device, but also preferably used as a unit battery in a medium-large battery module including a plurality of battery cells.
  • Preferred examples of the medium and large devices include, but are not limited to, electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, power storage systems, and the like.
  • a positive electrode active material powder was prepared in the same manner as in Example 1, except that (NH 4 ) 2 HPO 4 powder was used at 1.0 wt%.
  • a positive electrode active material slurry was prepared by mixing MNP so that the ratio of the positive electrode active material powder: conductive material: binder prepared in Example 1 was 95: 2.5: 2.5 (weight ratio), and the positive electrode active material slurry on aluminum foil having a thickness of 20 ⁇ m. was applied to a thickness of 200 ⁇ m, rolled and dried to prepare a positive electrode.
  • the anode was punched into a coin shape, and a coin-type battery was manufactured by using a carbonate electrolyte in which Li metal and LiPF 6 were melted as an anode.
  • a battery was manufactured in the same manner as in Example 1-1, except that the cathode active material powder prepared in Example 2 was used instead of the cathode active material powder prepared in Example 1.
  • a battery was manufactured in the same manner as in Example 1-1, except that the cathode active material powder prepared in Comparative Example 1 was used instead of the cathode active material powder prepared in Example 1.
  • a battery was manufactured in the same manner as in Example 1-1, except that the cathode active material powder prepared in Comparative Example 2 was used instead of the cathode active material powder prepared in Example 1.
  • a battery was manufactured in the same manner as in Example 1-1, except that the cathode active material powder prepared in Comparative Example 3 was used instead of the cathode active material powder prepared in Example 1.
  • the positive electrode active materials of Examples 1 and 2 doped with alkaline earth metal having +2 oxidized water according to the present invention and including a phosphate coating layer compared with the positive electrode active materials of Comparative Examples 1 to 3 Both Li 2 CO 3 by- products and LiOH by-products were found to be significantly reduced.
  • Li 2 CO 3 by- products and LiOH by-products in the positive electrode active materials of Examples 1 and 2 according to the present invention compared to Comparative Example 1 without doping Sr, which is an alkaline earth metal having +2 oxidized water, and do not include a phosphate coating layer. It was confirmed that the amount of significantly decreased.
  • the positive electrode active material according to the present invention has a low content of lithium byproducts (LiOH and Li 2 CO 3 ) which are basic impurities, the swelling phenomenon due to gas generation caused by reaction with the electrolyte during operation of the battery using the same is reduced. It can minimize and have structural stability can improve the life characteristics of the battery.
  • Each battery was charged at a rate of 0.1 C at CC / CV up to 4.24 V at 25 ° C., and then discharged at a rate of 0.1 C at CC up to 3.0 V to measure the charge and discharge capacity, thereby charging and discharging efficiency and discharge rate characteristics.
  • the ratio of 2.0 C discharge capacity (discharge rate) to 0.1 C was measured. The results are shown in Table 2 below.
  • the battery of Example 1-1 and Example 2-1 including the positive electrode active material according to the present invention includes a comparative example 1-1 to conventional lithium-nickel-based composite oxide positive electrode active material In comparison with the secondary battery of Comparative Example 3-1, it was confirmed that exhibited excellent initial capacity characteristics of the equivalent degree without deterioration.
  • Each battery was repeatedly charged and discharged 100 times under 1.0 C charge and 1.0 C discharge conditions at 45 ° C., and the capacity decay rate was measured according to the number of repetitions, and the results are shown in FIG. 1.
  • the battery of Example 1-1 and Example 2-1 using the positive electrode active material comprising a phosphorus coating layer and doped with Sr +2 is alkaline earth metal having oxidation number according to the present invention It was confirmed that the capacity retention rate was excellent during 100 charge / discharge cycles as compared with the batteries of Examples 1-1 to 3-1.
  • the battery of Example 1-1 showed a capacity of about 10% or more higher than that of Comparative Examples 1-1, 2-1, and 3-1 at 55 charge and discharge cycles, and at Comparative 100 charge / discharge cycles, A capacity of about 20% or more was higher than that of the batteries of 1-1 and 2-1, and about 15% or more higher than that of the battery of Comparative Example 3-1. That is, as the number of charge and discharge cycles increased, the difference in battery capacity between the batteries of Comparative Examples 1-1 and 3-1 and the batteries of Examples 1-1 and 2-1 further increased. Therefore, the capacity retention rate of the batteries of Example 1-1 and Example 2-1 according to the present invention was remarkably high, thereby confirming that the life characteristics are excellent.
  • the positive electrode active material according to the present invention includes a lithium-nickel-based transition metal composite oxide doped with an alkaline earth metal having a + 2-valent oxidation number and a phosphate coating layer formed on the outer surface of the composite oxide, thereby having the + 2-valent oxidation number
  • Alkaline earth metal acts as a kind of filler in the crystal lattice of the composite oxide to promote structural stability of the cathode active material and to reduce the natural loss of lithium cations, thereby reducing the generation of lithium byproducts.
  • the phosphate coating layer formed on the outer surface of the composite oxide reacts with the lithium byproduct present on the outer surface of the composite oxide to reduce the lithium byproduct, thereby suppressing swelling caused by the byproduct and preventing the formation of a resistive coating.
  • Storage Characteristics and Number of Batteries Containing Cathode Active Materials It means the improvement-rescue characteristics.

Abstract

The present invention relates to a cathode active material comprising: a lithium-nickel based transition metal composite oxide which is doped with an alkali earth metal having an oxidation state of +2; and a phosphorous oxide coating layer formed on the outer surface of the composite oxide, such that a lithium by-product is reduced and structural stability is improved. Accordingly, a secondary battery comprising the cathode active material has an excellent capacity property and at the same time, has improved structural stability during charging and discharging, and has a superior lifespan by suppressing swelling. Thus, the present invention can be easily applied to industries that require the present invention, particularly, to industries that require high capacity and a long-term lifespan of an electric vehicle and the like.

Description

리튬-니켈계 양극 활물질, 이의 제조방법 및 이를 포함하는 리튬 이차전지Lithium-nickel-based positive electrode active material, a method of manufacturing the same, and a lithium secondary battery comprising the same
본 발명은 리튬 부산물을 감소시키고 구조적 안정성을 향상시킨, +2가 산화수를 갖는 알칼리 토금속이 도핑된 리튬-니켈계 전이금속 복합 산화물 및 상기 복합 산화물 표면 상에 형성된 인산화물 코팅층을 포함하는 양극 활물질, 이를 포함하는 양극 및 상기 양극을 포함하는 이차전지에 관한 것이다.The present invention provides a positive electrode active material including a lithium-nickel-based transition metal composite oxide doped with alkaline earth metal having +2 oxidized water and a phosphate coating layer formed on the surface of the composite oxide, which reduces lithium by-products and improves structural stability. The present invention relates to a positive electrode including the same and a secondary battery including the positive electrode.
모바일 기기에 대한 기술 개발과 수요가 증가함에 따라 에너지원으로서 이차전지의 수요가 급격히 증가하고 있다. 이러한 이차전지 중 높은 에너지 밀도와 전압을 가지며, 사이클 수명이 길고 자기방전율이 낮은 리튬 이차전지가 상용화되어 널리 사용되고 있다. As technology development and demand for mobile devices increase, the demand for secondary batteries as a source of energy is rapidly increasing. Among such secondary batteries, lithium secondary batteries having high energy density and voltage, long cycle life, and low self discharge rate have been commercially used.
또한, 환경문제에 대한 관심이 커짐에 따라 대기오염의 주요 원인의 하나인 가솔린 차량, 디젤 차량 등 화석연료를 사용하는 차량을 대체할 수 있는 전기자동차, 하이브리드 전기자동차에 대한 관심이 높아지고 있으며, 이러한 전기자동차, 하이브리드 전기자동차 등의 동력원으로서 리튬 이차전지를 사용하기 위한 연구가 활발히 진행되고 있다.In addition, as interest in environmental problems increases, interest in electric vehicles and hybrid electric vehicles, which can replace vehicles using fossil fuel, such as gasoline and diesel vehicles, which are one of the main causes of air pollution, is increasing. Research into using lithium secondary batteries as a power source for electric vehicles and hybrid electric vehicles is being actively conducted.
리튬 이차전지를 전지자동차에 사용하기 위해서는, 높은 에너지 밀도와 단시간에 큰 출력을 발휘할 수 있는 특성을 가짐과 동시에, 가혹한 조건 하에서 10년 이상 사용될 수 있어야 하므로 기존의 소형 리튬 이차전지보다 월등히 우수한 안전성 및 장기 수명특성이 필연적으로 요구된다. In order to use a lithium secondary battery in a battery vehicle, it has to exhibit high energy density and a large output in a short time, and to be used for more than 10 years under severe conditions, so it has superior safety and safety than a conventional small lithium secondary battery. Long lifespan characteristics are inevitably required.
리튬 이차전지는 리튬 이온의 흡장 방출이 가능한 양극 활물질을 포함하고 있는 양극과, 리튬 이온의 흡장 방출이 가능한 음극 활물질을 포함하고 있는 음극, 상기 양극과 음극 사이에 미세 다공성 분리막이 개재된 전극 조립체에 리튬 이온을 함유한 비수 전해질이 포함되어 있는 전지를 의미한다. The lithium secondary battery includes a positive electrode including a positive electrode active material capable of occluding and releasing lithium ions, a negative electrode including a negative electrode active material capable of occluding and releasing lithium ions, and an electrode assembly having a microporous separator interposed between the positive electrode and the negative electrode. It means a battery containing a non-aqueous electrolyte containing lithium ions.
리튬 이차전지의 양극 활물질로는, 리튬 코발트 산화물(LiCoO2), 리튬-망간계 산화물(LiMn2O4) 또는 리튬-니켈 산화물(LiNiO2) 등의 전이금속 산화물, 이들 전이금속의 일부가 다른 전이금속으로 치환된 복합 산화물 등이 사용되고 있다. Examples of the positive electrode active material of a lithium secondary battery include transition metal oxides such as lithium cobalt oxide (LiCoO 2 ), lithium-manganese oxide (LiMn 2 O 4 ), or lithium-nickel oxide (LiNiO 2 ), and some of these transition metals are different. Composite oxides substituted with transition metals are used.
상기 양극 활물질들 중 LiCoO2는 우수한 사이클 특성 등 제반 물성이 우수하여 현재 많이 사용되고 있으나, 안전성이 낮으며 원료로서 코발트의 자원적 한계로 인해 고가이고, 전기자동차 등과 같은 분야의 동력원으로 대량 사용하기에는 한계가 있다. Among the positive electrode active materials, LiCoO 2 is widely used because of its excellent physical properties such as excellent cycle characteristics, but it is low in safety and expensive due to resource limitations of cobalt as a raw material, and is not suitable for mass use as a power source in fields such as electric vehicles. There is.
LiMnO2 또는 LiMn2O4 등의 리튬-망간계 산화물은 원료로서 자원이 풍부하고 환경친화적인 망간을 사용한다는 장점을 가지고 있어, LiCoO2를 대체할 수 있는 양극 활물질로서 많은 관심을 모으고 있으나, 이들 리튬-망간계 산화물은 용량이 작고, 사이클 특성 등이 좋지 못하는 단점을 가지고 있다. Lithium-manganese oxides such as LiMnO 2 or LiMn 2 O 4 have the advantage of using abundant resources and environmentally friendly manganese as raw materials, attracting much attention as a cathode active material that can replace LiCoO 2 , but Lithium-manganese oxides have disadvantages of low capacity and poor cycle characteristics.
반면에, LiNiO2 등의 리튬-니켈계 산화물은 상기 코발트계 산화물보다 비용이 저렴하면서도 4.3 V로 충전되었을 때, 높은 방전 용량을 나타내는바, 도핑된 LiNiO2의 가역 용량은 LiCoO2의 용량(약 165 mAh/g)을 초과하는 약 200 mAh/g에 근접한다.On the other hand, lithium-nickel-based oxides such as LiNiO 2 have a lower discharge cost than the cobalt-based oxides and have a high discharge capacity when charged at 4.3 V. Thus, the reversible capacity of the doped LiNiO 2 is about the capacity of LiCoO 2 (about 165 mAh / g) in excess of about 200 mAh / g).
따라서, 약간 낮은 평균 방전 전압과 체적 밀도(volumetric density)에도 불구하고, LiNiO2 양극 활물질을 포함하는 상용화 전지가 개선된 에너지 밀도를 나타내고 있어, 이러한 니켈계 양극 활물질을 이용한 고용량 전지의 개발 연구가 활발히 진행되고 있다. 그러나 리튬-니켈계 산화물은 고용량의 장점을 가지지만, 충방전 사이클에 동반하는 체적 변화에 따라 결정 구조의 급격한 상전이가 나타나고, 이에 따라 입자의 균열이나 결정입계에 공극이 발생하며, 저장 또는 사이클 동안 과량의 가스가 발생되고 공기와 습기에 노출되었을 때 표면에서 내화학성이 급격히 저하되는 등의 문제가 있어 실용화가 제한되고 있는 실정이다. Therefore, despite the slightly lower average discharge voltage and volumetric density, commercialized batteries including LiNiO 2 positive electrode active materials exhibit improved energy density, and thus, research into development of high capacity batteries using such nickel-based positive electrode active materials has been actively conducted. It's going on. However, lithium-nickel oxides have the advantage of high capacity, but due to the volume change accompanying the charge / discharge cycle, there is a sudden phase transition of the crystal structure, resulting in voids in the cracks or grain boundaries of the particles, and during storage or cycle When excessive gas is generated and exposed to air and moisture, there is a problem that the chemical resistance is sharply lowered on the surface, and thus the practical use is limited.
이에, 니켈의 일부를 망간, 코발트 등의 다른 전이금속으로 치환한 형태의 리튬 전이금속 산화물이 제안되었다. 그러나, 이러한 금속 치환된 니켈계 리튬 전이금속 산화물은 상대적으로 사이클 특성 및 용량 특성이 우수하다는 장점이 있지만, 이 경우에도 장기간 사용시에는 사이클 특성이 급격히 저하되고, 전지에서의 가스발생에 의한 스웰링, 낮은 화학적 안정성 등의 문제는 충분히 해결되지 못하고 있다. 따라서, 고용량화에 적합한 리튬 니켈계 양극 활물질을 이용하면서도 고온 안전성 문제를 해결할 수 있는 기술의 개발이 필요하다.Accordingly, lithium transition metal oxides in which a part of nickel is substituted with other transition metals such as manganese and cobalt have been proposed. However, these metal-substituted nickel-based lithium transition metal oxides have advantages in that they have relatively superior cycle characteristics and capacity characteristics, but even in this case, the cycle characteristics deteriorate rapidly during long-term use, and swelling by gas generation in a battery, Problems such as low chemical stability have not been sufficiently solved. Therefore, it is necessary to develop a technology capable of solving the high temperature safety problem while using a lithium nickel-based positive electrode active material suitable for high capacity.
또한, 리튬-니켈계 양극 활물질은 근본적으로 표면에 리튬 부산물(Li2CO3 및 LiOH) 발생이 높고, 이러한 리튬 부산물은 저항성 피막을 형성하고 양극 활물질 슬러리 제조 시 용매(예컨대 PVDF)와 반응하여 겔화를 일으킬 뿐 아니라 전지 내에서 가스를 발생하여 스웰링을 일으키며 이에 전지 수명특성을 크게 감소시키는 단점이 있다. In addition, the lithium-nickel positive electrode active material has a high generation of lithium by-products (Li 2 CO 3 and LiOH) on the surface, and these lithium by-products form a resistive film and react with a solvent (for example, PVDF) to prepare a cathode active material slurry to gel. Not only does it cause gas, but also generates swelling in the battery, which has the disadvantage of greatly reducing the battery life characteristics.
따라서, 표면처리 방법이나 도핑 등으로 표면을 안정화시키거나, 구조적 안정성을 개선하여 상기의 문제를 해결하기 위한 노력이 이어지고 있으나, 현재까지 효과적인 방법이 개발되지 못하고 있는 실정이다. Therefore, efforts have been made to solve the above problems by stabilizing the surface by surface treatment methods or doping, or improving structural stability, but an effective method has not been developed until now.
상기와 같은 배경 하에, 본 발명자들은 구조적 안정성을 향상시키고 리튬 부산물을 감소시킴으로써 부산물에서 야기되는 스웰링 및 저항성 피막 형성을 억제하여 전지 수명 특성을 향상시킬 수 있는 방법을 연구하던 중, 리튬-니켈계 전이금속 복합 산화물에 +2가의 산화수를 갖는 알칼리 토금속을 도핑하고, 상기 복합 산화물 표면에 인산화물 코팅층을 형성시켜 제조한 양극 활물질의 표면에 리튬 부산물이 현저히 감소함과 동시에 이를 포함하는 전지의 수명특성이 월등히 증가하는 것을 확인함으로써 본 발명을 완성하였다.Under the above background, the inventors of the present invention are studying a method of improving the structural stability and reducing lithium by-products, thereby suppressing the swelling and resistive film formation caused by the by-products, thereby improving battery life characteristics. Lithium by-products on the surface of the positive electrode active material prepared by doping an alkaline earth metal having a +2 valence oxidation number to a transition metal composite oxide and forming a phosphate coating layer on the surface of the composite oxide, and at the same time, life characteristics of a battery including the same The present invention was completed by confirming this increase.
본 발명의 목적은 리튬-니켈계 전이금속 복합 산화물 및 상기 복합 산화물 표면 상에 형성된 인산화물로 된 코팅층을 포함하는, 리튬 부산물이 감소되고 구조적 안정성이 향상된 양극 활물질을 제공하는 것이다.SUMMARY OF THE INVENTION An object of the present invention is to provide a cathode active material including a lithium-nickel transition metal composite oxide and a coating layer of phosphorous oxide formed on the surface of the composite oxide, with reduced lithium by-products and improved structural stability.
본 발명의 다른 목적은 상기의 양극 활물질의 제조방법을 제공하는 것이다. Another object of the present invention is to provide a method for producing the cathode active material.
본 발명의 또 다른 목적은 상기의 양극 활물질을 포함하는 양극 활물질 슬러리가 집전체에 도포된 이차전지용 양극을 제공하는 것이다. Still another object of the present invention is to provide a cathode for a secondary battery, in which a cathode active material slurry including the cathode active material is coated on a current collector.
더 나아가, 본 발명의 또 다른 목적은 상기의 이차전지용 양극, 음극, 상기 양극과 음극 사이에 개재된 분리막 및 전해질을 포함하는 수명 특성이 우수한 이차전지를 제공하는 것이다.Furthermore, another object of the present invention is to provide a secondary battery having excellent lifespan characteristics, including a separator and an electrolyte interposed between the positive electrode, the negative electrode, the positive electrode and the negative electrode for the secondary battery.
상기의 과제를 해결하기 위하여, 본 발명은 하기 화학식 1로 표시되는 층상구조의 리튬-니켈계 전이금속 복합 산화물; 및 상기 복합 산화물 표면 상에 형성된 인산화물로 이뤄진 코팅층을 포함하는 양극 활물질을 제공한다.In order to solve the above problems, the present invention is a lithium-nickel transition metal composite oxide having a layered structure represented by the formula (1); And it provides a cathode active material comprising a coating layer consisting of a phosphate oxide formed on the complex oxide surface.
[화학식 1][Formula 1]
LixNiaMbAwO2-yDy Li x Ni a M b A w O 2-y D y
상기 식에서, Where
1.0≤x≤1.2, 0.5≤a≤1, 0<b≤0.5, 0≤y<0.2, 0<w≤0.3이고, 2≤x+a+b+w≤2.2이며,1.0≤x≤1.2, 0.5≤a≤1, 0 <b≤0.5, 0≤y <0.2, 0 <w≤0.3, 2≤x + a + b + w≤2.2,
M은 Mn, Co, Cr, Fe, V 및 Zr로 이루어진 군으로부터 선택된 1종 이상의 원소이고,M is at least one element selected from the group consisting of Mn, Co, Cr, Fe, V and Zr,
A는 +2가 산화수를 갖는 하나 이상의 알칼리 토금속이며,A is at least one alkaline earth metal with +2 oxidation number,
D는 S, N, F, Cl, Br, I 및 P로 이루어진 군에서 선택된 1종 이상의 원소이다.D is at least one element selected from the group consisting of S, N, F, Cl, Br, I and P.
또한, 본 발명은 전이금속 전구체와 리튬 전구체의 혼합용액에 +2가의 산화수를 갖는 알칼리 토금속 전구체를 혼합하고 소결하여 상기 화학식 1로 표시되는 리튬-니켈계 전이금속 복합 산화물을 제조하는 단계(단계 1); 및 상기 복합 산화물에 인산화물 전구체를 혼합하고 소결하여, 상기 복합 산화물 외표면에 인산화물 코팅층을 형성시키는 단계(단계 2)를 포함하는 양극 활물질의 제조방법을 제공한다. In addition, the present invention is to prepare a lithium-nickel-based transition metal complex oxide represented by the formula (1) by mixing and sintering the alkaline earth metal precursor having a +2 valence oxidation number in the mixed solution of the transition metal precursor and the lithium precursor (step 1 ); And mixing and sintering a phosphate precursor to the complex oxide to form a phosphate coating layer on the outer surface of the complex oxide (step 2).
또한, 본 발명은 상기의 양극 활물질을 포함하는 양극 활물질 슬러리가 집전체 상에 도포되어 있는 이차전지용 양극을 제공한다.In addition, the present invention provides a secondary battery positive electrode, the positive electrode active material slurry containing the positive electrode active material is coated on the current collector.
아울러, 본 발명은 상기의 이차전지용 양극과 음극, 상기 양극과 음극 사이에 개재된 분리막 및 전해질을 포함하는 리튬 이차전지를 제공한다.In addition, the present invention provides a lithium secondary battery comprising a separator and an electrolyte interposed between the positive electrode and the negative electrode for the secondary battery, the positive electrode and the negative electrode.
본 발명에 따른 양극 활물질은 +2가 산화수를 갖는 알칼리 토금속이 도핑된 리튬-니켈계 전이금속 복합 산화물 및 상기 복합 산화물 외표면에 형성된 인산화물 코팅층을 포함함으로써, 상기 +2가 산화수를 갖는 알칼리 토금속(이의 양이온)이 상기 복합 산화물 내의 리튬 자리(리튬 양이온 자리) 또는 결정격자 내의 일부 빈공간에 위치하여 상기 결정격자 내에서 일종의 필러(pillar)로서 작용하여 상기 양극 활물질의 구조적 안정성을 도모하고, 리튬 양이온의 자연적 손실을 줄여 상기 리튬 양이온의 자연적 손실에 의하여 발생되는 리튬 부산물(LiOH 및 Li2CO3)의 생성을 감소시킬 수 있으며, 이와 동시에 상기 복합 산화물의 외표면을 둘러쌓고 있는 인산화물 코팅층이 상기 외표면에 존재하는 리튬 부산물과 반응하여 리튬 부산물을 감소시킴으로써, 리튬 부산물을 현저히 줄일 수 있어 상기 리튬 부산물로부터 야기되는 스웰링을 억제하고 저항성 피막 형성을 방지할 수 있다.The positive electrode active material according to the present invention includes a lithium-nickel-based transition metal composite oxide doped with an alkaline earth metal having +2 oxidation number and a phosphate coating layer formed on the outer surface of the composite oxide, thereby providing an alkaline earth metal having +2 oxidation number (The cation thereof) is located in a lithium site (lithium cation site) in the complex oxide or in some empty space in the crystal lattice to act as a kind of pillar in the crystal lattice to promote structural stability of the positive electrode active material, and By reducing the natural loss of the cation can reduce the production of lithium by-products (LiOH and Li 2 CO 3 ) generated by the natural loss of the lithium cation, and at the same time the phosphate coating layer surrounding the outer surface of the composite oxide By reacting with lithium by-products present on the outer surface to reduce lithium by-products, lithium By-products can be significantly reduced to suppress swelling resulting from the lithium by-products and to prevent resist film formation.
따라서, 본 발명에 따른 양극 활물질을 포함하는 이차전지는 우수한 용량 특성을 가짐과 동시에 충방전 시 구조적 안정성이 향상되고, 스웰링 현상이 억제되어 우수한 수명특성을 나타낼 수 있다. 이에, 이를 필요로 하는 산업, 특히 전기자동차 등의 고용량, 장기 수명특성을 필요로 하는 산업에 용이하게 적용할 수 있다.Therefore, the secondary battery including the cathode active material according to the present invention may have excellent capacity characteristics and structural stability during charging and discharging, and swelling may be suppressed to exhibit excellent life characteristics. Thus, the present invention can be easily applied to an industry requiring the high capacity and long lifespan of an electric vehicle.
본 명세서에 첨부되는 다음의 도면은 본 발명의 바람직한 실시예를 예시하는 것이며, 전술한 발명의 내용과 함께 본 발명의 기술 사상을 더욱 이해시키는 역할을 하는 것이므로, 본 발명은 그러한 도면에 기재된 사항에만 한정되어 해석되어서는 안된다.The following drawings, which are attached to this specification, illustrate exemplary embodiments of the present invention, and together with the contents of the present invention serve to further understand the technical idea of the present invention, the present invention is limited to the matters described in such drawings. It should not be construed as limited.
도 1은, 본 발명의 일 실시예에 따른 전지의 수명 특성 비교 결과 그래프를 나타낸 것이다.1 is a graph showing a result of comparing life characteristics of a battery according to an exemplary embodiment of the present invention.
이하, 본 발명에 대한 이해를 돕기 위하여 본 발명을 더욱 상세하게 설명한다.Hereinafter, the present invention will be described in more detail to aid in understanding the present invention.
본 명세서 및 청구범위에 사용된 용어나 단어는 통상적이거나 사전적인 의미로 한정해서 해석되어서는 아니 되며, 발명자는 그 자신의 발명을 가장 최선의 방법으로 설명하기 위해 용어의 개념을 적절하게 정의할 수 있다는 원칙에 입각하여 본 발명의 기술적 사상에 부합하는 의미와 개념으로 해석되어야만 한다. The terms or words used in this specification and claims are not to be construed as limiting in their usual or dictionary meanings, and the inventors may appropriately define the concept of terms in order to best explain their invention in the best way possible. It should be interpreted as meaning and concept corresponding to the technical idea of the present invention based on the principle that the present invention.
본 발명은 리튬-니켈계 전이금속 복합 산화물에 +2가 산화수를 갖는 알칼리 토금속을 도핑시키고, 인산화물 코팅층을 상기 복합 산화물 외표면에 형성시킴으로써 리튬 부산물을 감소시킴과 동시에 구조적 안정성을 향상시킨 양극 활물질을 제공한다. The present invention provides a positive electrode active material in which a lithium-nickel transition metal composite oxide is doped with an alkaline earth metal having a + 2-valent oxidation number, and a phosphate coating layer is formed on the outer surface of the composite oxide to reduce lithium by-products and improve structural stability. To provide.
본 발명의 일 실시예에 따른 상기 양극 활물질은 하기 화학식 1로 표시되는 층상구조의 리튬-니켈계 전이금속 복합 산화물; 및 상기 복합 산화물 외표면에 형성된 인산화물 코팅층을 포함하는 것을 특징으로 한다.The cathode active material according to an embodiment of the present invention is a lithium-nickel-based transition metal composite oxide having a layered structure represented by Formula 1 below; And a phosphate coating layer formed on the outer surface of the composite oxide.
[화학식 1][Formula 1]
LixNiaMbAwO2-yDy Li x Ni a M b A w O 2-y D y
상기 식에서, 1.0≤x≤1.2, 0.5≤a≤1, 0<b≤0.5, 0≤y<0.2, 0<w≤0.3이고, 2≤x+a+b+w≤2.2이며, M은 Mn, Co, Cr, Fe, V 및 Zr로 이루어진 군으로부터 선택된 1종 이상의 원소이고, A는 +2가 산화수를 갖는 하나 이상의 알칼리 토금속이며, D는 S, N, F, Cl, Br, I 및 P로 이루어진 군에서 선택된 1종 이상의 원소이다.In the above formula, 1.0≤x≤1.2, 0.5≤a≤1, 0 <b≤0.5, 0≤y <0.2, 0 <w≤0.3, 2≤x + a + b + w≤2.2, and M is Mn At least one element selected from the group consisting of Co, Cr, Fe, V and Zr, A is at least one alkaline earth metal with +2 oxidation number, D is S, N, F, Cl, Br, I and P At least one element selected from the group consisting of.
상기 양극 활물질은 리튬-니켈계 산화물(LiNiO2)을 베이스로 하는 것으로, 상기 화학식 1에서 M으로 표시되는 원소를 첨가함으로써 구조적 불안정성을 보완할 수 있으며, A로 표시되는 원소를 도핑함으로써 구조적 불안정성을 보완함과 동시에 리튬 양이온의 자연적 손실을 억제할 수 있어 이에 의해 발생하는 리튬 부산물을 감소시킬 수 있다. 이때 니켈(Ni)과 M 및 A로 표시되는 원소의 몰 비에 따라 전기화학적 특성이 크게 변화할 수 있다. 따라서, 상기 니켈(Ni)과 M 및 A로 표시되는 원소의 몰 비를 적절하게 조율하는 것이 중요할 수 있다.The cathode active material is based on lithium-nickel oxide (LiNiO 2 ), and can supplement structural instability by adding an element represented by M in Chemical Formula 1, and structural doping by doping an element represented by A At the same time, the natural loss of lithium cations can be suppressed, thereby reducing the amount of lithium by-products generated. At this time, the electrochemical properties may vary greatly according to the molar ratio of the elements represented by nickel (Ni) and M and A. Therefore, it may be important to properly adjust the molar ratio of the elements represented by nickel (Ni) and M and A.
구체적으로, 상기 양극 활물질에서 상기 니켈(Ni)의 함량은 리튬을 제외한 금속 성분 전체량, 즉 상기 화학식 1에서 Ni, M 및 A로 표시되는 원소의 총량을 기준으로 70 mol% 이상일 수 있으며, 바람직하게는 75 mol% 이상일 수 있다. Specifically, the content of the nickel (Ni) in the positive electrode active material may be 70 mol% or more based on the total amount of metal components excluding lithium, that is, the total amount of elements represented by Ni, M, and A in Formula 1, and Preferably at least 75 mol%.
또한, 상기 M으로 표시되는 원소는 앞서 언급한 원소 중 하나 또는 둘 이상일 수 있으나, 바람직하게는 상기 M은 Mnb1Cob2일 수 있으며, 여기서, 0<b1+b2≤0.5, 바람직하게는 0<b1+b2≤0.3일 수 있다.In addition, the element represented by M may be one or two or more of the aforementioned elements, preferably, M may be Mn b1 Co b2 , where 0 <b1 + b2 ≦ 0.5, preferably 0 < b1 + b2 ≦ 0.3.
만약, 상기 양극 활물질에 포함되는 니켈의 함량이 70 mol% 이상이고, 상기 M으로 표시되는 원소가 상기 나타낸 조건을 만족할 경우, 상기의 양극 활물질을 포함하는 이차전지의 방전전압 및 용량특성 등의 전지 특성이 우수할 수 있다.If the amount of nickel contained in the positive electrode active material is 70 mol% or more, and the element represented by M satisfies the conditions described above, the battery may be discharged and capacity characteristics of the secondary battery including the positive electrode active material. Properties may be excellent.
상기 A로 표시되는 원소는 상기 양극 활물질 내 리튬층에서의 니켈 양이온의 혼입을 방지하지 위하여 리튬 자리(리튬 양이온 자리)에 도핑된 것으로, 상기 A는 +2가 산화수를 갖는 알칼리 토금속으로 상기 니켈 양이온 보다 큰 이온반경을 갖는 특성이 있다. The element represented by A is doped in a lithium site (lithium cation site) in order to prevent mixing of the nickel cation in the lithium layer in the positive electrode active material, wherein A is an alkaline earth metal having +2 oxidation number and the nickel cation There is a characteristic of having a larger ion radius.
구체적으로, 상기 A로 표시되는 +2가 산화수를 갖는 알칼리 토금속은 상기 양극 활물질의 결정구조에서 리튬 자리(리튬 양이온 자리) 또는 결정격자 내의 빈공간에 위치할 수 있으며, 이에 전하균형을 이룰 수 있어 니켈 양이온이 리튬 양이온 자리로 혼입되는 양이온 혼합(cation mixing)을 억제할 수 있으며, 결정격자 내에서 일종의 필러(pillar)로서 작용함으로써 상기 양극 활물질의 구조적 안정성을 도모하고, 리튬 양이온의 자연적 손실을 줄일 수 있다. 이에 결과적으로, 상기의 양극 활물질을 포함하는 이차전지의 충방전 시 구조적 안정성을 향상시킴과 동시에 리튬 양이온의 자연적 손실에 의해 발생하는 부산물(LiOH 및 Li2CO3)의 생성을 억제할 수 있으며, 상기 부산물에 의한 스웰링을 감소시켜 전지의 수명특성을 향상시키는 역할을 할 수 있다.Specifically, the alkaline earth metal having a +2 oxidation number represented by A may be located in a lithium site (lithium cation site) or an empty space in a crystal lattice in the crystal structure of the cathode active material, thereby achieving charge balance. It is possible to suppress cation mixing in which nickel cations are incorporated into lithium cation sites, and act as a kind of filler in the crystal lattice to promote structural stability of the cathode active material and to reduce natural loss of lithium cations. Can be. As a result, it is possible to improve the structural stability during charging and discharging of the secondary battery including the cathode active material and to suppress the generation of by-products (LiOH and Li 2 CO 3 ) generated by the natural loss of lithium cations. It may serve to improve the life characteristics of the battery by reducing the swelling by the by-products.
상기 화학식 1에서 A로 표시되는 +2가 산화수를 갖는 알칼리 토금속은 Sr인 것이 바람직할 수 있다. It may be preferable that the alkaline earth metal having an oxidation number of +2 represented by A in Formula 1 is Sr.
또한, 상기 화학식 1에서 D는 -1가 또는 -2가의 산화수를 갖는 음이온으로, 상기 화학식 1에서 산소이온은 소정의 범위에서 상기의 음이온으로 치환될 수 있다. In addition, in Chemical Formula 1, D is an anion having an oxidation number of -1 or -2, and oxygen ions in Chemical Formula 1 may be substituted with the anion in a predetermined range.
상기의 음이온은 앞서 언급한 바와 같이 S, N, F, Cl, Br, I 및 P로 이루어진 군에서 선택된 1종 이상의 원소일 수 있으며, 이러한 음이온의 치환에 의하여 전이금속과의 결합력이 향상되고 양극 활물질 내에서의 구조 전이가 방지될 수 있어, 결과적으로 전지의 수명특성을 향상시킬 수 있다. 그러나, 상기 음이온의 치환량이 너무 많으면(y≥0.2) 불완전한 결정구조를 형성하여, 오히려 전지의 수명특성을 저하시킬 수 있다. As described above, the anion may be at least one element selected from the group consisting of S, N, F, Cl, Br, I, and P. The substitution of the anion may improve the bonding strength with the transition metal and the positive electrode Structural transition in the active material can be prevented, resulting in improved life characteristics of the battery. However, if the amount of substitution of the anion is too large (y ≧ 0.2), an incomplete crystal structure may be formed, which may lower the lifespan of the battery.
상기 양극 활물질은 상기 언급한 바와 같이, 상기 화학식 1로 표시되는 리튬-니켈계 전이금속 복합 산화물 외표면에 형성된 인산화물 코팅층을 포함하는 것을 특징으로 한다. 또한, 상기 인산화물 코팅층은 수 나노미터 내지 수십 나노미터 이상의 두께를 가질 수 있으며, 구체적으로는 상기 두께는 1 nm 내지 100 nm일 수 있다.As described above, the cathode active material includes a phosphate coating layer formed on the outer surface of the lithium-nickel-based transition metal composite oxide represented by Chemical Formula 1. In addition, the phosphate coating layer may have a thickness of several nanometers to several tens of nanometers or more, and specifically, the thickness may be 1 nm to 100 nm.
상기 인산화물 코팅층은 상기 복합 산화물의 외표면에 존재하는 리튬 부산물, 즉 LiOH 및 Li2CO3와 반응하여 Li3PO4를 형성함으로써 리튬 부산물을 감소시켜 상기 부산물로부터 야기되는 스웰링을 억제하고 저항성 피막 형성을 방지할 수 있으며, 상기 화학식 1로 표시되는 리튬-니켈계 전이금속 복합 산화물과 반응하여 전이금속 층 내에 하기 화학식 2로 표시되는 구조를 포함하는 반응물을 형성함으로써 상기 양극 활물질의 구조적 안정성을 높일 수 있다. 이에, 상기의 양극 활물질을 포함하는 이차전지의 저장특성 및 수명특성을 개선시킬 수 있다.The phosphate coating layer reacts with lithium by-products present on the outer surface of the composite oxide, that is, LiOH and Li 2 CO 3 to form Li 3 PO 4 to reduce lithium by-products, thereby inhibiting swelling caused by the by-products and being resistant. It is possible to prevent the formation of the film, and by reacting with the lithium-nickel-based transition metal complex oxide represented by the formula (1) to form a reactant comprising a structure represented by the formula (2) in the transition metal layer to improve the structural stability of the positive electrode active material It can increase. Thus, the storage characteristics and lifespan characteristics of the secondary battery including the cathode active material may be improved.
[화학식 2][Formula 2]
Li(Li3e±fM'1-fPe)O2+z Li (Li 3e ± f M ' 1-f P e ) O 2 + z
상기 식에서, 0<e<0.1, 0<f<0.3, -4e<z≤4e이고, 3e-y일때 3e>y이며, M'는 NiaMbAw이고 여기에서 M, A, a, b 및 w는 앞서 언급한 바와 같다.Wherein 0 <e <0.1, 0 <f <0.3, -4e <z≤4e, 3e> y when 3e-y, and M 'is Ni a M b A w where M, A, a, b and w are as mentioned above.
상기 인산화물의 원료물질인 인산화물 전구체는 (NH4)2HPO4, (NH4)2H2PO4, (NH4)3PO4·3H2O, H3PO4 및 P2O5으로 이루어진 군으로부터 선택된 1종 이상인 것일 수 있으며, 바람직하게는 (NH4)2HPO4일 수 있다.Phosphorus precursors that are raw materials of the phosphate include (NH 4 ) 2 HPO 4 , (NH 4 ) 2 H 2 PO 4 , (NH 4 ) 3 PO 4 · 3H 2 O, H 3 PO 4 and P 2 O 5 It may be one or more selected from the group consisting of, preferably (NH 4 ) 2 HPO 4 It may be.
또한, 본 발명은 리튬 부산물을 감소시키고 구조적 안정성을 향상시킨 상기의 양극 활물질의 제조방법을 제공한다.In addition, the present invention provides a method for producing the positive electrode active material to reduce the lithium by-products and improve the structural stability.
본 발명의 일 실시예에 따른 상기 양극 활물질의 제조방법은 전이금속 전구체와 리튬 전구체의 혼합용액에 +2가의 산화수를 갖는 알칼리 토금속 전구체를 혼합하고 소결하여 상기 화학식 1로 표시되는 리튬-니켈계 전이금속 복합 산화물을 제조하는 단계(단계 1); 및 상기 리튬-니켈계 전이금속 복합 산화물에 인산화물 전구체를 첨가하고 소결하여, 상기 복합 산화물 외표면에 인산화물 코팅층을 형성시키는 단계(단계 2)를 포함하는 것을 특징으로 한다. In the method of manufacturing the cathode active material according to an embodiment of the present invention, a lithium-nickel-based transition represented by Chemical Formula 1 is obtained by mixing and sintering an alkaline earth metal precursor having +2 valence oxidation number in a mixed solution of a transition metal precursor and a lithium precursor. Preparing a metal complex oxide (step 1); And adding a phosphate precursor to the lithium-nickel-based transition metal composite oxide and sintering it to form a phosphate coating layer on the outer surface of the composite oxide (step 2).
상기 단계 1은, 상기 화학식 1로 표시되는 알칼리 토금속이 도핑된 리튬-니켈계 전이금속 복합 산화물을 제조하기 위한 단계로, 특별히 한정되지 않고 당업계에 통상적으로 알려진 방법에 의하여 제조할 수 있으나, 예컨대 고상반응법, 공침법, 졸-겔법, 수열합성법 등을 통하여 제조할 수 있다. Step 1 is a step for preparing a lithium-nickel-based transition metal composite oxide doped with an alkaline earth metal represented by Chemical Formula 1, and is not particularly limited, but may be prepared by a method commonly known in the art. It may be prepared by a solid phase reaction method, coprecipitation method, sol-gel method, hydrothermal synthesis method and the like.
구체적으로, 상기 리튬-니켈계 전이금속 복합 산화물은 상기 니켈계 전이금속 복합 산화물을 구성하는 니켈 전구체, 니켈을 제외한 전이금속 전구체 각각을 용매에 용해한 후 공침시켜 전이금속 복합 수산화물을 제조하고, 여기에 리튬 전구체를 첨가하여 혼합용액을 제조한 후 +2가의 산화수를 갖는 알칼리 토금속 전구체를 혼합하고 소결하여 제조할 수 있다. Specifically, the lithium-nickel transition metal composite oxide is prepared by dissolving a nickel precursor constituting the nickel-based transition metal composite oxide and a transition metal precursor except for nickel in a solvent, followed by coprecipitation, to prepare a transition metal composite hydroxide. After preparing a mixed solution by adding a lithium precursor, it can be prepared by mixing and sintering an alkaline earth metal precursor having an oxidation number of +2.
상기 전이금속 복합 수산화물은 Me(OH1-x)2(0≤x≤0.5)로 표시되는 것일 수 있으며, Me는 전이금속을 나타내는 것으로 상기 화학식 1에서 NiaMb로 표시되는 것이다. The transition metal complex hydroxide may be represented by Me (OH 1-x ) 2 (0 ≦ x ≦ 0.5), and Me represents a transition metal and is represented by Ni a M b in Chemical Formula 1.
또한, 상기 니켈 전구체, 니켈을 제외한 전이금속 전구체 및 +2가의 산화수를 갖는 알칼리 토금속 전구체는 앞서 언급한 바와 같이 리튬을 제외한 금속 성분 전체량에 대하여 니켈이 70 mol% 이상이 되도록 조절하여 사용하는 것이 바람직할 수 있다. In addition, the nickel precursor, the transition metal precursor except nickel, and the alkaline earth metal precursor having a +2 valence oxidation number, as mentioned above, are used by adjusting the nickel to be 70 mol% or more with respect to the total amount of the metal components except lithium. It may be desirable.
상기 단계 1에서의 소결은 700℃ 내지 900℃의 온도에서 20시간 내지 30시간 동안 열처리하여 수행한 것일 수 있으나, 이에 제한되는 것은 아니다. The sintering in step 1 may be performed by heat treatment for 20 hours to 30 hours at a temperature of 700 ℃ to 900 ℃, but is not limited thereto.
상기 전이금속 전구체 및 리튬 전구체는 특별히 한정되지 않고, 각 금속의 염의 형태인 것일 수 있으며, 예컨대 나이트레이트(nitrate), 설페이트(sulfate), 카보네이트(carbonate), 하이드록사이드(hydroxide), 아세테이트(acetate), 옥살레이트(oxalate), 클로라이드(chloride) 등의 형태일 수 있다.The transition metal precursor and the lithium precursor are not particularly limited, and may be in the form of a salt of each metal, for example, nitrate, sulfate, carbonate, hydroxide, acetate, and acetate. ), Oxalate, chloride, and the like.
또한, 상기 +2가의 산화수를 갖는 알칼리 토금속 전구체는 알칼리 토금속 염일 수 있으며, 구체적으로는 SrCO3일 수 있다.In addition, the alkaline earth metal precursor having an oxidation number of +2 may be an alkaline earth metal salt, and specifically, may be SrCO 3 .
상기 단계 2는, 상기 단계 1에서 제조된 알칼리 토금속이 도핑된 리튬-니켈계 전이금속 복합 산화물 외표면에 인산화물 코팅층을 형성시켜, 리튬 부산물이 적고 구조적 안정성이 우수한 양극 활물질을 제조하기 위한 단계로, 상기 리튬-니켈계 전이금속 복합 산화물에 인산화물 전구체를 첨가하고 소결하여 수행할 수 있다.Step 2 is to form a phosphate coating layer on the outer surface of the lithium-nickel-based transition metal composite oxide doped with alkaline earth metal prepared in step 1, to produce a cathode active material having less lithium by-product and excellent structural stability In addition, a phosphate precursor may be added to the lithium-nickel-based transition metal composite oxide and sintered.
상기 단계 2에서의 소결은 100℃ 내지 700℃의 온도에서 10시간 이내로 열처리하여 수행한 것일 수 있으며, 구체적으로는 상기 열처리는 1분 내지 10시간 범위 내의 시간 동안 수행한 것일 수 있다. The sintering in step 2 may be performed by heat treatment within 10 hours at a temperature of 100 ℃ to 700 ℃, specifically, the heat treatment may be performed for a time within the range of 1 minute to 10 hours.
상기 인산화물 전구체는 앞서 언급한 바와 같거나, 포함되는 것일 수 있다.The phosphate precursor may be as mentioned above or included.
또한, 본 발명은 상기의 양극 활물질을 포함하는 양극 슬러리가 집전체 상에 도포되어 있는 이차전지용 양극을 제공한다.In addition, the present invention provides a positive electrode for a secondary battery in which a positive electrode slurry containing the positive electrode active material is coated on a current collector.
본 발명의 일 실시예에 따른 상기 양극은 상기 양극 활물질을 포함하는 양극 활물질 슬러리를 양극 집전체에 도포하고 건조 및 압연하여 제조할 수 있다. The positive electrode according to an embodiment of the present invention may be prepared by applying a positive electrode active material slurry containing the positive electrode active material to a positive electrode current collector, drying and rolling.
상기 양극 집전체는 일반적으로 3 ㎛ 내지 500 ㎛의 두께인 것을 사용할 수 있으며, 당해 전지에 화학적 변화를 유발하지 않으면서 높은 도전성을 가지는 것이라면 특별히 제한되는 것은 아니나, 예컨대 스테인레스 스틸, 알루미늄, 니켈, 티탄, 소성 탄소 또는 알루미늄이나 스테인레스 스틸의 표면에 카본, 니켈, 티탄 또는 은 등으로 표면 처리한 것 등이 사용될 수 있다. The positive electrode current collector may be generally used having a thickness of 3 ㎛ to 500 ㎛, and is not particularly limited as long as it has a high conductivity without causing chemical changes in the battery, for example, stainless steel, aluminum, nickel, titanium , Surface treated with carbon, nickel, titanium or silver on the surface of calcined carbon or aluminum or stainless steel may be used.
상기 양극 활물질 슬러리는 상기 양극 활물질에 바인더와 도전재 및 충진제와 분산제 등의 첨가제를 첨가하고 혼합하여 제조한 것일 수 있다.The positive electrode active material slurry may be prepared by adding and mixing an additive such as a binder, a conductive material, a filler, and a dispersant to the positive electrode active material.
상기 바인더는 상기 양극 활물질과 도전재의 결합과 집전체에 대한 결합에 조력하는 성분으로서, 통상적으로 양극 활물질 총량을 기준으로 1 중량% 내지 30 중량%로 첨가될 수 있다. 이러한 바인더는 특별히 한정되지 않고 당업계에 공지된 통상적인 것을 사용할 수 있으나, 예컨대 비닐리덴플루오라이드-헥사플루오로프로필렌 코폴리머(PVBF-co-HEP), 폴리비닐리덴플루오라이드(polyvinylidenefluoride), 폴리아크릴로니트릴(polyacrylonitrile), 폴리메틸메타크릴레이트(polymethylmethacrylate), 폴리비닐알코올, 카르복시메틸셀룰로오스(CMC), 전분, 히드록시프로필셀룰로오스, 재생 셀룰로오스, 폴리비닐피롤리돈, 테트라플루오로에틸렌, 폴리에틸렌, 폴리프로필렌, 폴리아크릴산, 에틸렌-프로필렌-디엔 모노머(EPDM), 술폰화 EPDM, 스티렌-부티렌 고무(SBR) 및 불소 고무로 이루어진 군으로부터 선택된 1종 또는 2종 이상의 혼합물일 수 있다. The binder is a component that assists the bonding between the positive electrode active material and the conductive material and the current collector, and may generally be added in an amount of 1 wt% to 30 wt% based on the total amount of the positive electrode active material. Such binders are not particularly limited and may be conventional ones known in the art, but include, for example, vinylidene fluoride-hexafluoropropylene copolymer (PVBF-co-HEP), polyvinylidenefluoride, and polyacryl. Ronitrile (polyacrylonitrile), polymethylmethacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, poly 1 or 2 or more types selected from the group consisting of propylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene-butyrene rubber (SBR) and fluorine rubber.
상기 도전재는 통상적으로 양극 활물질 전체 중량을 기준으로 0.05 중량% 내지 5 중량%로 첨가될 수 있다. 이러한 도전재는 특별히 한정되지 않고 전지의 기타 요소들과 부반응을 유발하지 않으면서 도전성을 가진 것이라면 특별히 제한되는 것은 아니나, 예컨대 천연 흑연이나 인조 흑연 등의 흑연; 카본 블랙(super-p), 아세틸렌 블랙, 케첸 블랙, 채널 블랙, 퍼네이스 블랙, 램프 블랙, 서머 블랙 등의 카본 블랙; 탄소 섬유나 금속 섬유 등의 도전성 섬유; 불화 카본, 알루미늄, 니켈 분말 등의 금속 분말; 산화아연, 티탄산 칼륨 등의 도전성 위스커; 산화 티탄 등의 도전성 금속 산화물; 폴리페닐렌 유도체 등의 도전성 소재 등일 수 있다. The conductive material may be added at 0.05 wt% to 5 wt% based on the total weight of the positive electrode active material. Such a conductive material is not particularly limited and is not particularly limited as long as it is conductive without causing side reactions with other elements of the battery. Examples thereof include graphite such as natural graphite and artificial graphite; Carbon blacks such as carbon black (super-p), acetylene black, ketjen black, channel black, furnace black, lamp black and summer black; Conductive fibers such as carbon fibers and metal fibers; Metal powders such as carbon fluoride powder, aluminum powder and nickel powder; Conductive whiskers such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives.
상기 충진제는 양극의 팽창을 억제하는 성분으로서 필요에 따라 사용 여부를 정할 수 있으며, 당해 전지에 화학적 변화를 유발하지 않으면서 섬유상 재료라면 특별히 제한되는 것은 아니나, 예컨대 폴리에틸렌 폴리프로필렌 등의 올리핀계 중합체; 유리섬유, 탄소섬유 등의 섬유상 물질일 수 있다. The filler may be used as necessary to determine whether or not to be used as a component to suppress the expansion of the positive electrode, and is not particularly limited as long as it is a fibrous material without causing chemical change in the battery, for example, olefin polymers such as polyethylene polypropylene; It may be a fibrous material such as glass fiber, carbon fiber.
상기 분산제(분산액)로는 특별히 한정되는 것은 아니나, 예컨대 이소프로필 알코올, N-메틸피롤리돈(NMP), 아세톤 등일 수 있다. The dispersant (dispersion) is not particularly limited, but may be, for example, isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or the like.
상기 도포는 당업계에 통상적으로 공지된 방법에 의하여 수행할 수 있으나, 예컨대 상기 양극 활물질 슬러리를 상기 양극 집전체 일측 상면에 분배시킨 후 닥터 블레이드(doctor blade) 등을 사용하여 균일하게 분산시켜 수행할 수 있다. 이외에도, 다이 캐스팅(die casting), 콤마 코팅(comma coating), 스크린 프린팅(screen printing) 등의 방법을 통하여 수행할 수 있다. The coating may be performed by a method commonly known in the art, but for example, the positive electrode active material slurry may be distributed on an upper surface of one side of the positive electrode current collector, and then uniformly dispersed using a doctor blade or the like. Can be. In addition, the method may be performed by a die casting method, a comma coating method, a screen printing method, or the like.
상기 건조는 특별히 한정되는 것은 아니나 50℃ 내지 200℃의 진공오븐에서 1일 이내로 수행하는 것일 수 있다. The drying is not particularly limited, but may be performed within one day in a vacuum oven at 50 ℃ to 200 ℃.
아울러, 본 발명은 상기의 이차전지용 양극과 음극, 상기 양극과 음극 사이에 개재된 분리막 및 전해질을 포함하는 리튬 이차전지를 제공한다.In addition, the present invention provides a lithium secondary battery comprising a separator and an electrolyte interposed between the positive electrode and the negative electrode for the secondary battery, the positive electrode and the negative electrode.
본 발명의 일 실시예에 따른 상기 리튬 이차전지는 리튬-니켈계 전이금속 복합 산화물에 +2가 산화수를 갖는 알칼리 토금속을 도핑시키고, 인산화물 코팅층을 표면에 형성시킴으로써 리튬 부산물을 감소시키고 구조적 안정성을 향상시킨 양극 활물질을 포함하는 양극과 음극, 상기 양극과 음극 사이에 개재된 분리막 및 전해질을 포함하는 것을 특징으로 한다. In the lithium secondary battery according to an embodiment of the present invention, a lithium-nickel transition metal composite oxide is doped with an alkaline earth metal having a +2 oxidation number, and a phosphate coating layer is formed on the surface to reduce lithium by-products and improve structural stability. And a separator and an electrolyte interposed between the positive electrode and the negative electrode including the improved positive electrode active material, the positive electrode and the negative electrode.
또한, 상기 리튬 이차전지는 45℃에서 1.0 C 충전 및 1.0 C 방전 조건의 55회 사이클(cycle)에서 초기 용량 대비 용량 유지율이 90% 이상인 것을 특징으로 한다.In addition, the lithium secondary battery has a capacity retention ratio of 90% or more at initial capacity in 55 cycles of 1.0 C charge and 1.0 C discharge conditions at 45 ° C.
상기 음극은 특별히 한정되는 것은 아니나, 음극 집전체 일측 상면에 음극 활물질을 포함하는 음극 활물질 슬러리를 도포한 후 건조하여 제조할 수 있으며, 상기 음극 활물질 슬러리는 음극 활물질 이외에 바인더 및 도전재와 충진제 및 분산제와 같은 첨가제를 포함할 수 있다. The negative electrode is not particularly limited, but may be prepared by coating a negative electrode active material slurry containing a negative electrode active material on one side of a negative electrode current collector and then drying it. The negative electrode active material slurry may include a binder, a conductive material, a filler, and a dispersant in addition to the negative electrode active material. It may include additives such as.
상기 음극 집전체는 앞서 언급한 양극 집전체와 동일한 것이거나, 포함되는 것일 수 있다.The negative electrode current collector may be the same as or included in the aforementioned positive electrode current collector.
상기 음극 활물질은 특별히 한정되지 않고 당업계에 통상적으로 공지된 리튬 이온이 흡장 및 방출될 수 있는 탄소재, 리튬 금속, 규소 또는 주석 등을 사용할 수 있다. 바람직하게는 탄소재를 사용할 수 있으며, 탄소재로는 저결정 탄소 및 고결정성 탄소 등이 모두 사용될 수 있다. 저결정성 탄소로는 연화탄소(soft carbon) 및 경화탄소(hard carbon)를 들 수 있으며, 고결정성 탄소로는 천연 흑연, 키시흑연(kish graphite), 열분해 탄소(pyrolytic carbon), 액정치피계 탄소섬유(mesophase pitch based carbon fiber), 탄소 미소구체(meso-carbon microbeads), 액정피치(mesophase pitches) 및 석유와 석탄계 코크스(petroleum or coal tar pitch derived cokes) 등의 고온 소성탄소를 들 수 있다. The negative electrode active material is not particularly limited and may be a carbon material, lithium metal, silicon, tin, or the like in which lithium ions commonly known in the art may be occluded and released. Preferably, a carbon material may be used, and as the carbon material, both low crystalline carbon and high crystalline carbon may be used. Low crystalline carbon includes soft carbon and hard carbon, and high crystalline carbon includes natural graphite, kish graphite, pyrolytic carbon, liquid crystalline carbon High temperature calcined carbon such as fibers (mesophase pitch based carbon fiber), meso-carbon microbeads, liquid crystal pitch (mesophase pitches) and petroleum or coal tar pitch derived cokes.
상기 음극에 사용되는 바인더 및 도전재와 충진제 및 분산제와 같은 첨가제는 앞서 언급한 양극 제조에 사용된 것과 동일하거나, 포함되는 것일 수 있다.Additives such as binders, conductive materials, fillers, and dispersants used in the negative electrode may be the same as or included in the aforementioned positive electrode.
상기 분리막으로는 높은 이온 투과도와 기계적 강도를 가지는 절연성의 얇은 박막일 수 있으며, 일반적으로 0.01 ㎛ 내지 10 ㎛의 기공직경, 5 ㎛ 내지 300 ㎛의 두께를 갖는 것일 수 있다. 이러한 분리막으로는 다공성 고분자 필름, 예컨대 에틸렌 단독중합체, 프로필렌 단독중합체, 에틸렌/부텐 공중합체, 에틸렌/헥센 공중합체 및 에틸렌/메타크릴레이트 공중합체 등과 같은 폴리올레핀계 고분자로 제조한 다공성 고분자 필름을 단독으로 또는 이들을 적층하여 사용할 수 있으며, 또는 통상적인 다공성 부직포, 예를 들어 고융점의 유리 섬유, 폴리에틸렌테레프탈레이트 섬유 등으로 된 부직포를 사용할 수 있으나, 이에 제한되는 것은 아니다. The separator may be an insulating thin film having high ion permeability and mechanical strength, and may generally have a pore diameter of 0.01 μm to 10 μm and a thickness of 5 μm to 300 μm. As such a separator, a porous polymer film made of a polyolefin-based polymer such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, ethylene / methacrylate copolymer, etc. may be used alone. Alternatively, these may be laminated and used, or a nonwoven fabric made of a conventional porous nonwoven fabric, for example, a high melting glass fiber, polyethylene terephthalate fiber, or the like may be used, but is not limited thereto.
또한, 상기 전해질은 전해질에 통상적으로 사용되는 유기용매 및 리튬염을 포함할 수 있으며, 특별히 제한되는 것은 아니다. In addition, the electrolyte may include an organic solvent and a lithium salt commonly used in the electrolyte, and are not particularly limited.
상기 리튬염의 음이온으로는 F-, Cl-, I-, NO3 -, N(CN)2 -, BF4 -, ClO4 -, PF6 -, (CF3)2PF4 -, (CF3)3PF3 -, (CF3)4PF2 -, (CF3)5PF-, (CF3)6P-, CF3SO3 -, CF3CF2SO3 -, (CF3SO2)2N-, (FSO2)2N-, CF3CF2(CF3)2CO-, (CF3SO2)2CH-, (SF5)3C-, (CF3SO2)3C-, CF3(CF2)7SO3 -, CF3CO2 -, CH3CO2 -, SCN- 및 (CF3CF2SO2)2N-로 이루어진 군으로부터 선택되는 1종 이상일 수 있다.With the lithium salt of the anion is F -, Cl -, I - , NO 3 -, N (CN) 2 -, BF 4 -, ClO 4 -, PF 6 -, (CF 3) 2 PF 4 -, (CF 3 ) 3 PF 3 -, (CF 3) 4 PF 2 -, (CF 3) 5 PF -, (CF 3) 6 P -, CF 3 SO 3 -, CF 3 CF 2 SO 3 -, (CF 3 SO 2 ) 2 N -, (FSO 2 ) 2 N -, CF 3 CF 2 (CF 3) 2 CO -, (CF 3 SO 2) 2 CH -, (SF 5) 3 C -, (CF 3 SO 2) 3 C -, CF 3 (CF 2 ) 7 SO 3 -, CF 3 CO 2 -, CH 3 CO 2 -, SCN - , and (CF 3 CF 2 SO 2) 2 N - be at least one selected from the group consisting of have.
상기 유기용매로는 대표적으로 프로필렌 카보네이트, 에틸렌 카보네이트, 디에틸카보네이트, 디메틸카보네이트, 에틸메틸카보네이트, 메틸프로필카보네이트, 디프로필카보네이트, 디메틸술폭사이드, 아세토니트릴, 디메톡시에탄, 디에톡시에탄, 비닐렌카보네이트, 술포란, 감마-부티로락톤, 프로필렌설파이트 및 테트라하이드로퓨란으로 이루어진 군으로부터 선택되는 1종 이상인 것일 수 있다. Typical organic solvents include propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, dipropyl carbonate, dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxy ethane and vinylene carbonate. , Sulfolane, gamma-butyrolactone, propylene sulfite and tetrahydrofuran may be one or more selected from the group consisting of.
특히, 상기 카보네이트계 유기용매 중 고리형 카보네이트인 에틸렌카보네이트 및 프로필렌카보네이트는 고점도의 유기용매로서 유전율이 높아 전해질 내의 리튬염을 잘 해리시키므로 바람직하게 사용될 수 있으며, 이러한 고리형 카보네이트 디메틸카보네이트 및 디에틸카보네이트와 같은 저점도, 저유전율 선형 카보네이트를 적당한 비율로 혼합하여 사용하면 높은 전기 전도율을 갖는 전해액을 만들 수 있어 더욱 바람직하게 사용될 수 있다. In particular, ethylene carbonate and propylene carbonate, which are cyclic carbonates among the carbonate-based organic solvents, are highly viscous organic solvents, and thus may be preferably used because they dissociate lithium salts in electrolytes well. By using a low viscosity, low dielectric constant linear carbonate, such as mixed in an appropriate ratio it can be more preferably used to make an electrolyte having a high electrical conductivity.
또한, 상기 전해질은 필요에 따라 충방전 특성, 난연성 특성 등의 개선을 위하여 피리딘, 트리에틸포스파이트, 트리에탄올아민, 환상 에테르, 에틸렌 디아민, n-글라임(glyme), 헥사 인산 트리 아미드, 니트로벤젠 유도체, 유황, 퀴논 이민 염료, N-치환 옥사졸리디논, N,N-치환 이미다졸리딘, 에틸렌 글리콜 디알킬 에테르, 암모늄염, 피롤, 2-메톡시 에탄올, 삼염화 알루미늄 등을 추가로 포함할 수 있다. 경우에 따라서는, 불연성을 부여하기 위하여 사염화탄소, 삼불화에틸렌 등의 할로겐 함유 용매를 더 포함할 수 있으며, 고온 보존 특성을 향상시키기 위하여 이산화탄산 가스를 더 포함할 수도 있고, FEC(fluoro-ethylene carbonate), PRS(propene sultone), FPC(fluoro-prpylene carbonate) 등을 더 포함할 수 있다. In addition, the electrolyte may be pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, hexa phosphate triamide, nitrobenzene to improve the charge and discharge characteristics, flame retardancy characteristics, etc. as necessary. Derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N, N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrroles, 2-methoxy ethanol, aluminum trichloride, and the like. have. In some cases, the solvent may further include a halogen-containing solvent such as carbon tetrachloride or ethylene trifluoride to impart nonflammability, may further include carbon dioxide gas to improve high temperature storage characteristics, and may further include fluoro-ethylene carbonate. ), Propene sultone (PRS), and fluoro-prpylene carbonate (FPC).
본 발명의 리튬 이차전지는 양극과 음극 사이에 분리막을 배치하여 전극 조립체를 형성하고, 상기 전극 조립체는 원통형 전지 케이스 또는 각형 전지 케이스에 넣은 다음 전해질을 주입하여 제조할 수 있다. 또는, 상기 전극 조립체를 적층한 후, 이를 전해질에 함침시키고 얻어진 결과물을 전지 케이스에 넣어 밀봉하여 제조할 수도 있다.In the lithium secondary battery of the present invention, an electrode assembly is formed by disposing a separator between a positive electrode and a negative electrode, and the electrode assembly may be manufactured by putting an electrolyte into a cylindrical battery case or a square battery case. Alternatively, after stacking the electrode assembly, it may be prepared by impregnating it in an electrolyte and sealing the resultant obtained in a battery case.
본 발명에서 사용되는 전지 케이스는 당분야에서 통상적으로 사용되는 것이 채택될 수 있고, 전지의 용도에 따른 외형에 제한이 없으며, 예를 들면, 캔을 사용한 원통형, 각형, 파우치(pouch)형 또는 코인(coin)형 등이 될 수 있다.The battery case used in the present invention may be adopted that is commonly used in the art, there is no limitation on the appearance according to the use of the battery, for example, cylindrical, square, pouch type or coin using a can (coin) type and the like.
본 발명에 따른 리튬 이차전지는 소형 디바이스의 전원으로 사용되는 전지셀에 사용될 수 있을 뿐만 아니라, 다수의 전지셀들을 포함하는 중대형 전지모듈에 단위전지로도 바람직하게 사용될 수 있다. 상기 중대형 디바이스의 바람직한 예로는 전기자동차, 하이브리드 전기자동차, 플러그-인 하이브리드 전기자동차, 전력 저장용 시스템 등을 들 수 있지만, 이들 만으로 한정되는 것은 아니다.The lithium secondary battery according to the present invention may not only be used in a battery cell used as a power source for a small device, but also preferably used as a unit battery in a medium-large battery module including a plurality of battery cells. Preferred examples of the medium and large devices include, but are not limited to, electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, power storage systems, and the like.
이하, 본 발명을 구체적으로 설명하기 위해 실시예를 들어 상세하게 설명하기로 한다. 그러나, 본 발명에 따른 실시예는 여러 가지 다른 형태로 변형될 수 있으며, 본 발명의 범위가 아래에서 상술하는 실시예에 한정되는 것으로 해석되어서는 안 된다. 본 발명의 실시예는 당업계에서 평균적인 지식을 가진 자에게 본 발명을 보다 완전하게 설명하기 위해서 제공되는 것이다.Hereinafter, the present invention will be described in detail with reference to Examples. However, embodiments according to the present invention can be modified in many different forms, the scope of the present invention should not be construed as limited to the embodiments described below. The embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art.
실시예 1Example 1
전이금속 전구체로서 Ni0.78Mn0.11Co0.11OOH를 준비하고, 여기에 LiOH을 Li/전이금속=1 몰당량 비율로 혼합하여 혼합물을 제조하고, 상기 혼합물 기준 0.2 중량%의 SrCO3를 첨가하고 혼합한 후 800℃에서 24시간 동안 소성하여 Sr이 도핑된 리튬-니켈계 전이금속 복합 산화물 분말을 제조하였다. 상기 복합 산화물 기준 0.5 중량%의 (NH4)2HPO4 분말을 혼합하고 500℃의 온도에서 열처리하고 채질(400 호)하여 양극 활물질 분말을 제조하였다. Ni 0.78 Mn 0.11 Co 0.11 OOH was prepared as a transition metal precursor, and LiOH was mixed at a Li / transition metal = 1 molar equivalent ratio to prepare a mixture, and 0.2% by weight of SrCO 3 based on the mixture was added and mixed. After firing at 800 ℃ for 24 hours to prepare a lithium-nickel transition metal composite oxide powder doped with Sr. 0.5 wt% (NH 4 ) 2 HPO 4 powder based on the composite oxide was mixed, heat treated at 500 ° C., and filled (No. 400) to prepare a cathode active material powder.
실시예 2Example 2
(NH4)2HPO4 분말을 1.0 중량%로 사용한 것을 제외하고는 상기 실시예 1과 동일한 방법을 통하여 양극 활물질 분말을 제조하였다. A positive electrode active material powder was prepared in the same manner as in Example 1, except that (NH 4 ) 2 HPO 4 powder was used at 1.0 wt%.
비교예 1Comparative Example 1
전이금속 전구체로서 Ni0.78Mn0.11Co0.11OOH를 준비하고, 여기에 LiOH을 Li/전이금속=1 몰당량 비율로 혼합하고 800℃에서 24시간 동안 소성하여 양극 활물질 분말을 제조하였다. As a transition metal precursor prepared a Ni 0.78 Co 0.11 OOH Mn0 .11, which was then mixed with LiOH herein by Li / transition metal molar equivalents ratio = 1 was prepared the positive electrode active material powder was calcined at 800 ℃ for 24 hours.
비교예 2Comparative Example 2
전이금속 전구체로서 Ni0.78Mn0.11Co0.11O0H를 준비하고, 여기에 LiOH을 Li/전이금속=1 몰당량 비율로 혼합하여 혼합물을 제조하고, 상기 혼합물 기준 0.2 중량%의 SrCO3를 첨가하고 혼합한 후 800℃에서 24시간 동안 소성하여 양극 활물질 분말을 제조하였다. Ni 0.78 Mn 0.11 Co 0.11 O0H was prepared as a transition metal precursor, and LiOH was mixed at a Li / transition metal = 1 molar equivalent ratio to prepare a mixture, and 0.2% by weight of SrCO 3 based on the mixture was added and mixed. After firing at 800 ℃ for 24 hours to prepare a positive electrode active material powder.
비교예 4Comparative Example 4
전이금속 전구체로서 Ni0.78Mn0.11Co0.11OOH를 준비하고, 여기에 LiOH을 Li/전이금속=1 몰당량 비율로 혼합하고 800℃에서 24시간 동안 소성하여 리튬-니켈계 전이금속 복합 산화물 분말을 제조하였다. 상기 복합 산화물 기준 0.5 중량%의 (NH4)2HPO4 분말을 혼합하고 500℃의 온도에서 열처리하고 채질(400 호)하여 양극 활물질 분말을 제조하였다. Ni 0.78 Mn 0.11 Co 0.11 OOH was prepared as a transition metal precursor, and LiOH was mixed in a Li / transition metal = 1 molar equivalent ratio and calcined at 800 ° C. for 24 hours to prepare a lithium-nickel transition metal composite oxide powder. It was. 0.5 wt% (NH 4 ) 2 HPO 4 powder based on the composite oxide was mixed, heat treated at 500 ° C., and filled (No. 400) to prepare a cathode active material powder.
실시예 1-1Example 1-1
상기 실시예 1에서 제조한 양극 활물질 분말 : 도전재 : 바인더의 비율이 95 : 2.5 : 2.5(중량비)가 되도록 MNP에 혼합하여 양극 활물질 슬러리를 제조하고, 20 ㎛ 두께의 알루미늄 호일에 상기 양극 활물질 슬러리를 200 ㎛ 두께로 도포한 후 압연 및 건조하여 양극을 제조하였다. A positive electrode active material slurry was prepared by mixing MNP so that the ratio of the positive electrode active material powder: conductive material: binder prepared in Example 1 was 95: 2.5: 2.5 (weight ratio), and the positive electrode active material slurry on aluminum foil having a thickness of 20 μm. Was applied to a thickness of 200 ㎛, rolled and dried to prepare a positive electrode.
상기 양극을 코인 모양으로 타발하고, 음극으로 Li 금속, 전해질로 LiPF6가 1몰 녹아있는 카보네이트 전해액을 이용하여 코인 형태의 전지를 제작하였다. The anode was punched into a coin shape, and a coin-type battery was manufactured by using a carbonate electrolyte in which Li metal and LiPF 6 were melted as an anode.
실시예 2-1Example 2-1
상기 실시예 1에서 제조한 양극 활물질 분말 대신에 실시예 2에서 제조한 양극 활물질 분말을 사용한 것을 제외하고는 상기 실시예 1-1과 동일한 방법을 통하여 전지를 제작하였다. A battery was manufactured in the same manner as in Example 1-1, except that the cathode active material powder prepared in Example 2 was used instead of the cathode active material powder prepared in Example 1.
비교예 1-1Comparative Example 1-1
상기 실시예 1에서 제조한 양극 활물질 분말 대신에 비교예 1에서 제조한 양극 활물질 분말을 사용한 것을 제외하고는 상기 실시예 1-1과 동일한 방법을 통하여 전지를 제작하였다. A battery was manufactured in the same manner as in Example 1-1, except that the cathode active material powder prepared in Comparative Example 1 was used instead of the cathode active material powder prepared in Example 1.
비교예 2-1Comparative Example 2-1
상기 실시예 1에서 제조한 양극 활물질 분말 대신에 비교예 2에서 제조한 양극 활물질 분말을 사용한 것을 제외하고는 상기 실시예 1-1과 동일한 방법을 통하여 전지를 제작하였다. A battery was manufactured in the same manner as in Example 1-1, except that the cathode active material powder prepared in Comparative Example 2 was used instead of the cathode active material powder prepared in Example 1.
비교예 3-1Comparative Example 3-1
상기 실시예 1에서 제조한 양극 활물질 분말 대신에 비교예 3에서 제조한 양극 활물질 분말을 사용한 것을 제외하고는 상기 실시예 1-1과 동일한 방법을 통하여 전지를 제작하였다. A battery was manufactured in the same manner as in Example 1-1, except that the cathode active material powder prepared in Comparative Example 3 was used instead of the cathode active material powder prepared in Example 1.
실험예 1Experimental Example 1
상기 실시예 1과 2 및 비교예 1 내지 3에서 제조한 각 양극 활물질 분말 표면에 미반응된 상태로 남아있는 리튬 부산물(Li2CO3 및 LiOH)의 양을 비교 분석하기 위하여, pH 적정법을 이용하여 각 양극 활물질 분말 표면에 존재하는 리튬 부산물 양을 측정하였다. In order to analyze the amount of lithium by-products (Li 2 CO 3 and LiOH) remaining unreacted on the surface of each of the positive electrode active material powders prepared in Examples 1 and 2 and Comparative Examples 1 to 3, a pH titration method was used. The amount of lithium byproducts present on the surface of each cathode active material powder was measured.
상기 pH 적정은 상기 실시예 1 및 2와 비교예 1 내지 3의 각 양극 활물질 분말 5 g을 각각 물 25 ㎖에 넣고 교반한 후, 디켄팅(decanting)하여 투명용액 약 20 ㎖를 분말로부터 분리하여 모았다. 다시 25 ㎖의 물을 상기 분말에 가하여 교반하며 디켄팅한 후 투명용액을 모았다. 이러한 방식으로 소킹(soaking)과 디켄팅을 반복하여 수용성 염기를 함유한 투명용액 100 ㎖를 모은 후 교반하면서 0.1 M HCl 용액을 상기 투명용액에 적가하여 pH 적정을 수행하였다. 적정실험은 pH=3 이하의 값에 도달하였을 때 종료하였으며, 유속은 적정이 약 20 내지 30분 소요되는 범위로 적절히 조절하였다. 수용성 염기의 함량은 pH<5에 도달할 때까지 사용된 산의 양으로 측정하고 이로부터 분말 표면의 염기성 불순물 함량을 계산하였다. 결과를 하기 표 1에 나타내었다.In the pH titration, 5 g of the positive electrode active material powders of Examples 1 and 2 and Comparative Examples 1 to 3 were added to 25 ml of water, stirred, and then decanted to separate about 20 ml of the transparent solution from the powder. Collected. Again 25 ml of water was added to the powder, followed by decantation with stirring to collect the clear solution. Soaking and decanting were repeated in this manner to collect 100 ml of a transparent solution containing a water-soluble base, and then, pH stirring was performed by dropwise adding 0.1 M HCl solution to the transparent solution while stirring. The titration experiment was terminated when the value reached pH = 3 or less, and the flow rate was appropriately adjusted in the range that the titration took about 20 to 30 minutes. The content of water soluble base was measured by the amount of acid used until pH <5 was reached and from this the basic impurity content of the powder surface was calculated. The results are shown in Table 1 below.
표 1
구분 실시예 1 실시예 2 비교예 1 비교예 2 비교예 3
Li2CO3(중량%) 0.110 0.071 0.118 0.170 0.101
LiOH(중량%) 0.166 0.151 0.305 0.211 0.210
총 리튬 부산물(중량%) 0.276 0.222 0.423 0.381 0.311
Table 1
division Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3
Li 2 CO 3 (% by weight) 0.110 0.071 0.118 0.170 0.101
LiOH (% by weight) 0.166 0.151 0.305 0.211 0.210
Total lithium byproduct (% by weight) 0.276 0.222 0.423 0.381 0.311
상기 표 1에 나타난 바와 같이, 본 발명에 따른 +2가 산화수를 갖는 알칼리 토금속을 도핑하고, 인산화물 코팅층을 포함하는 실시예 1 및 2의 양극 활물질이 비교예 1 내지 3의 양극 활물질과 비교하여 Li2CO3 부산물 및 LiOH 부산물 모두 현저히 감소한 것을 확인하였다. As shown in Table 1, the positive electrode active materials of Examples 1 and 2 doped with alkaline earth metal having +2 oxidized water according to the present invention and including a phosphate coating layer compared with the positive electrode active materials of Comparative Examples 1 to 3 Both Li 2 CO 3 by- products and LiOH by-products were found to be significantly reduced.
구체적으로, +2가 산화수를 갖는 알칼리 토금속인 Sr을 도핑하지 않고 인산화물 코팅층을 포함하지 않는 비교예 1에 비하여 본 발명에 따른 실시예 1 및 2의 양극 활물질에서 Li2CO3 부산물 및 LiOH 부산물의 양이 현저히 감소하였음을 확인하였다. Specifically, Li 2 CO 3 by- products and LiOH by-products in the positive electrode active materials of Examples 1 and 2 according to the present invention compared to Comparative Example 1 without doping Sr, which is an alkaline earth metal having +2 oxidized water, and do not include a phosphate coating layer. It was confirmed that the amount of significantly decreased.
또한, Sr은 도핑하였으나, 인산화물 코팅층을 포함하지 않는 비교예 2 및 인산화물 코팅층은 포함하나, Sr은 도핑하지 않은 비교예 3의 양극 활물질에 비해서도 본 발명에 따른 실시예 1 및 실시예 2의 양극 활물질에서 리튬 부산물의 양이 현저히 감소하였음을 확인하였다. 이는, 본 발명에 따른 양극 활물질이 +2가의 산화수를 갖는 알칼리 토금속을 도핑하고 인산화물 코팅층을 포함함으로써 더욱 효과적으로 리튬 부산물을 감소시킬 수 있음을 의미한다. In addition, Sr is doped, but Comparative Example 2 and the phosphate coating layer that does not include a phosphate coating layer, but Sr of Example 1 and Example 2 according to the present invention compared to the positive electrode active material of Comparative Example 3 which is not doped It was confirmed that the amount of lithium byproducts in the cathode active material was significantly reduced. This means that the positive electrode active material according to the present invention can more effectively reduce lithium by-products by doping alkaline earth metals having + 2-valent oxidation number and including a phosphate coating layer.
따라서, 본 발명에 따른 양극 활물질은 염기성 불순물인 리튬 부산물(LiOH 및 Li2CO3)의 함량이 적기 때문에, 이를 이용한 전지의 작동 시 전해액과의 반응으로 인해 야기되는 가스 발생으로 인한 스웰링 현상을 최소화할 수 있으며, 구조적 안정성을 가질 수 있어 전지의 수명 특성을 향상시킬 수 있다. Therefore, since the positive electrode active material according to the present invention has a low content of lithium byproducts (LiOH and Li 2 CO 3 ) which are basic impurities, the swelling phenomenon due to gas generation caused by reaction with the electrolyte during operation of the battery using the same is reduced. It can minimize and have structural stability can improve the life characteristics of the battery.
실험예 2Experimental Example 2
상기 실시예 1-1 및 2-1과 비교예 1-1 내지 3-1에서 제작한 각 전지의 초기 용량 특성을 비교 분석하였다. Initial capacity characteristics of the batteries prepared in Examples 1-1 and 2-1 and Comparative Examples 1-1 to 3-1 were compared and analyzed.
상기 각 전지를 25℃에서 4.24 V까지 CC/CV로 0.1 C의 속도로 충전한 후, 3.0 V까지 CC로 0.1C의 속도로 방전하여 충전 및 방전 용량을 측정하고 이를 통하여 충방전 효율 및 방전율 특성을 분석하였다. 또한, 0.1 C 대비 2.0 C 방전 용량 비율(방전율)을 측정하였다. 결과를 하기 표 2에 나타내었다.Each battery was charged at a rate of 0.1 C at CC / CV up to 4.24 V at 25 ° C., and then discharged at a rate of 0.1 C at CC up to 3.0 V to measure the charge and discharge capacity, thereby charging and discharging efficiency and discharge rate characteristics. Was analyzed. In addition, the ratio of 2.0 C discharge capacity (discharge rate) to 0.1 C was measured. The results are shown in Table 2 below.
표 2
구분 실시예1-1 실시예2-1 비교예1-1 비교예2-1 비교예3-1
충정용량(mAh/g) 216 215 214 217 215
방전용량(mAh/g) 188 188 188 188 187
충방전효율(%) 87.2 87.3 87.2 86.7 87.0
방전율(%, 2.0C/0.1C) 88.9 88.9 89.1 89.0 88.8
TABLE 2
division Example 1-1 Example 2-1 Comparative Example 1-1 Comparative Example 2-1 Comparative Example 3-1
Charge capacity (mAh / g) 216 215 214 217 215
Discharge Capacity (mAh / g) 188 188 188 188 187
Charge and discharge efficiency (%) 87.2 87.3 87.2 86.7 87.0
Discharge Rate (%, 2.0C / 0.1C) 88.9 88.9 89.1 89.0 88.8
상기 표 2에 나타난 바와 같이, 본 발명에 따른 양극 활물질을 포함하는 실시예 1-1 및 실시예 2-1의 전지가 종래의 리튬-니켈계 복합 산화물 양극 활물질을 포함하는 비교예 1-1 내지 비교예 3-1의 이차전지와 비교하여 성능 저하 없이 동등한 정도의 우수한 초기 용량 특성을 나타내는 것을 확인하였다. As shown in Table 2, the battery of Example 1-1 and Example 2-1 including the positive electrode active material according to the present invention includes a comparative example 1-1 to conventional lithium-nickel-based composite oxide positive electrode active material In comparison with the secondary battery of Comparative Example 3-1, it was confirmed that exhibited excellent initial capacity characteristics of the equivalent degree without deterioration.
실험예 3Experimental Example 3
상기 실시예 1-1 및 실시예 2-1과 비교예 1-1 내지 3-1의 각 전지의 수명특성을 비교분석 하였다. The life characteristics of the batteries of Examples 1-1 and 2-1 and Comparative Examples 1-1 to 3-1 were compared and analyzed.
각 전지를 45℃에서 1.0 C 충전 및 1.0 C 방전 조건하에서 100회 충방전을 반복하고, 반복 횟수에 따른 용량 퇴화도를 측정하였으며, 그 결과를 도 1에 나타내었다. Each battery was repeatedly charged and discharged 100 times under 1.0 C charge and 1.0 C discharge conditions at 45 ° C., and the capacity decay rate was measured according to the number of repetitions, and the results are shown in FIG. 1.
도 1에 나타난 바와 같이, 본 발명에 따른 +2가 산화수를 갖는 알칼리 토금속인 Sr을 도핑하고, 인산화물 코팅층을 포함하는 양극 활물질을 이용한 실시예 1-1 및 실시예 2-1의 전지가 비교예 1-1 내지 3-1의 전지와 비교하여 100회 충방전 동안 용량 유지율이 우수한 것을 확인하였다. As shown in Figure 1, the battery of Example 1-1 and Example 2-1 using the positive electrode active material comprising a phosphorus coating layer and doped with Sr +2 is alkaline earth metal having oxidation number according to the present invention It was confirmed that the capacity retention rate was excellent during 100 charge / discharge cycles as compared with the batteries of Examples 1-1 to 3-1.
특히, 실시예 1-1의 전지의 경우 55회 충반전에서 비교예 1-1, 2-1 및 3-1의 전지에 비하여 약 10% 이상 높은 용량을 나타내었으며, 100회 충방전에서는 비교예 1-1 및 2-1의 전지에 비해서는 약 20% 이상 그리고 비교예 3-1의 전지와 비교해서는 약 15% 이상 높은 용량을 나타내었다. 즉, 충방전 횟수의 증가에 따라 비교예 1-1 내기 3-1의 전지와 상기 실시예 1-1 및 2-1의 전지의 전지 용량 차이가 더욱 증가하였다. 따라서, 본 발명에 따른 실시예 1-1 및 실시예 2-1의 전지의 용량 유지율이 현저히 높으며, 이에 수명 특성이 월등히 우수함을 확인하였다. In particular, the battery of Example 1-1 showed a capacity of about 10% or more higher than that of Comparative Examples 1-1, 2-1, and 3-1 at 55 charge and discharge cycles, and at Comparative 100 charge / discharge cycles, A capacity of about 20% or more was higher than that of the batteries of 1-1 and 2-1, and about 15% or more higher than that of the battery of Comparative Example 3-1. That is, as the number of charge and discharge cycles increased, the difference in battery capacity between the batteries of Comparative Examples 1-1 and 3-1 and the batteries of Examples 1-1 and 2-1 further increased. Therefore, the capacity retention rate of the batteries of Example 1-1 and Example 2-1 according to the present invention was remarkably high, thereby confirming that the life characteristics are excellent.
이는, 본 발명에 따른 양극 활물질이 +2가의 산화수를 갖는 알칼리 토금속이 도핑된 리튬-니켈계 전이금속 복합 산화물 및 상기 복합 산화물 외표면에 형성된 인산화물 코팅층을 포함함으로써, 상기 +2가의 산화수를 갖는 알칼리 토금속이 상기 복합 산화물의 결정격자 내에서 일종의 필러(pillar)로서 작용하여 상기 양극 활물질의 구조적 안정성을 도모하고, 리튬 양이온의 자연적 손실을 줄여 이로부터 발생되는 리튬 부산물의 생성을 감소시켰으며, 이와 동시에 상기 복합 산화물 외표면에 형성된 인산화물 코팅층이 상기 복합 산화물 외표면에 존재하는 리튬 부산물과 반응하여 상기 리튬 부산물을 감소시켜 상기 부산물로부터 야기되는 스웰링을 억제하고 저항성 피막 형성을 방지하여 결과적으로 상기 양극 활물질을 포함하는 전지의 저장특성 및 수명특성을 개선시켰음을 의미한다.This is because the positive electrode active material according to the present invention includes a lithium-nickel-based transition metal composite oxide doped with an alkaline earth metal having a + 2-valent oxidation number and a phosphate coating layer formed on the outer surface of the composite oxide, thereby having the + 2-valent oxidation number Alkaline earth metal acts as a kind of filler in the crystal lattice of the composite oxide to promote structural stability of the cathode active material and to reduce the natural loss of lithium cations, thereby reducing the generation of lithium byproducts. At the same time, the phosphate coating layer formed on the outer surface of the composite oxide reacts with the lithium byproduct present on the outer surface of the composite oxide to reduce the lithium byproduct, thereby suppressing swelling caused by the byproduct and preventing the formation of a resistive coating. Storage Characteristics and Number of Batteries Containing Cathode Active Materials It means the improvement-rescue characteristics.

Claims (16)

  1. 하기 화학식 1로 표시되는 층상구조의 리튬-니켈계 전이금속 복합 산화물; 및 상기 복합 산화물 표면 상에 형성된 인산화물 코팅층을 포함하는 양극 활물질:A lithium-nickel transition metal composite oxide having a layered structure represented by Formula 1 below; And a phosphate coating layer formed on the complex oxide surface:
    [화학식 1][Formula 1]
    LixNiaMbAwO2-yDy Li x Ni a M b A w O 2-y D y
    상기 식에서, Where
    1.0≤x≤1.2, 0.5≤a≤1, 0<b≤0.5, 0≤y<0.2, 0<w≤0.3이고, 2≤x+a+b+w≤2.2이며,1.0≤x≤1.2, 0.5≤a≤1, 0 <b≤0.5, 0≤y <0.2, 0 <w≤0.3, 2≤x + a + b + w≤2.2,
    M은 Mn, Co, Cr, Fe, V 및 Zr로 이루어진 군으로부터 선택된 1종 이상의 원소이고,M is at least one element selected from the group consisting of Mn, Co, Cr, Fe, V and Zr,
    A는 +2가 산화수를 갖는 하나 이상의 알칼리 토금속 원소이며,A is at least one alkaline earth metal element with +2 oxidation number,
    D는 S, N, F, Cl, Br, I 및 P로 이루어진 군에서 선택된 1종 이상의 원소이다.D is at least one element selected from the group consisting of S, N, F, Cl, Br, I and P.
  2. 청구항 1에 있어서,The method according to claim 1,
    상기 양극 활물질에서 상기 니켈의 함량은 리튬을 제외한 금속 성분 전체량을 기준으로 70 mol% 이상인 것을 특징으로 하는 양극 활물질.The amount of the nickel in the positive electrode active material is a positive electrode active material, characterized in that more than 70 mol% based on the total amount of metal components excluding lithium.
  3. 청구항 1에 있어서,The method according to claim 1,
    상기 화학식 1에서 M은 Mnb1Cob2이고, In Formula 1, M is Mn b1 Co b2 ,
    여기서, 0<b1+b2≤0.5 인 것을 특징으로 하는 양극 활물질.Here, 0 <b1 + b2≤0.5, The positive electrode active material characterized by the above-mentioned.
  4. 청구항 1에 있어서,The method according to claim 1,
    상기 화학식 1에서 A로 표시되는 금속 원소는 리튬 자리 또는 결정격자 내의 빈공간에 위치하는 것을 특징으로 하는 양극 활물질.The metal element represented by A in Chemical Formula 1 is located in an empty space in a lithium site or a crystal lattice.
  5. 청구항 1에 있어서,The method according to claim 1,
    상기 화학식 1에서 A는 Sr인 것을 특징으로 하는 양극 활물질.In Chemical Formula 1, A is Sr.
  6. 청구항 1에 있어서,The method according to claim 1,
    상기 인산화물의 원료 물질인 인산화물 전구체는 (NH4)2HPO4, (NH4)2H2PO4, (NH4)3PO4·(3H2O), H3PO4 및 P2O5으로 이루어진 군으로부터 선택된 1종 이상인 것을 특징으로 하는 양극 활물질.Phosphorus precursors that are raw materials of the phosphate include (NH 4 ) 2 HPO 4 , (NH 4 ) 2 H 2 PO 4 , (NH 4 ) 3 PO 4 · (3H 2 O), H 3 PO 4, and P 2 Cathode active material, characterized in that at least one member selected from the group consisting of O 5 .
  7. 청구항 1에 있어서,The method according to claim 1,
    상기 인산화물 코팅층은 1 nm 내지 100 nm의 두께를 갖는 것을 특징으로 하는 양극 활물질.The phosphate coating layer is a positive electrode active material, characterized in that having a thickness of 1 nm to 100 nm.
  8. 1) 전이금속 전구체와 리튬 전구체의 혼합용액에 +2가의 산화수를 갖는 알칼리 토금속 전구체를 혼합하고 소결하여 하기 화학식 1로 표시되는 리튬-니켈계 전이금속 복합 산화물을 제조하는 단계; 및1) preparing a lithium-nickel-based transition metal complex oxide represented by the following Chemical Formula 1 by mixing and sintering an alkaline earth metal precursor having +2 valence oxidation number in a mixed solution of a transition metal precursor and a lithium precursor; And
    2) 상기 복합 산화물에 인산화물 전구체를 혼합하고 소결하여, 상기 복합 산화물 표면 상에 인산화물 코팅층을 형성시키는 단계를 포함하는 양극 활물질의 제조방법:2) a method of manufacturing a cathode active material comprising mixing and sintering a phosphate precursor to the complex oxide to form a phosphate coating layer on the surface of the complex oxide;
    [화학식 1][Formula 1]
    LixNiaMbAwO2-yDy Li x Ni a M b A w O 2-y D y
    상기 식에서,Where
    1.0≤x≤1.2, 0.5≤a≤1, 0<b≤0.5, 0≤y<0.2, 0<w≤0.3이고, 2≤x+a+b+w≤2.2이며,1.0≤x≤1.2, 0.5≤a≤1, 0 <b≤0.5, 0≤y <0.2, 0 <w≤0.3, 2≤x + a + b + w≤2.2,
    M은 Mn, Co, Cr, Fe, V 및 Zr로 이루어진 군으로부터 선택된 1종 이상의 원소이고,M is at least one element selected from the group consisting of Mn, Co, Cr, Fe, V and Zr,
    A는 +2가 산화수를 갖는 하나 이상의 알칼리 토금속 원소이며,A is at least one alkaline earth metal element with +2 oxidation number,
    D는 S, N, F, Cl, Br, I 및 P로 이루어진 군에서 선택된 1종 이상의 원소이다.D is at least one element selected from the group consisting of S, N, F, Cl, Br, I and P.
  9. 청구항 8에 있어서,The method according to claim 8,
    상기 전이금속 전구체는 Me(OH1-x)2(0≤x≤0.5)이고,The transition metal precursor is Me (OH 1-x ) 2 (0 ≦ x ≦ 0.5),
    여기서, Me는 상기 화학식 1에서 NiaMb로 표시되는 것인 것을 특징으로 하는 양극 활물질의 제조방법.Here, Me is a method for producing a positive electrode active material, characterized in that represented by Ni a M b in the formula (1).
  10. 청구항 8에 있어서,The method according to claim 8,
    상기 단계 1)의 소결은 700℃ 내지 900℃의 온도에서 20시간 내지 30시간 동안 열처리한 것인 것을 특징으로 하는 양극 활물질의 제조방법.The sintering of step 1) is a method for producing a positive electrode active material, characterized in that the heat treatment for 20 to 30 hours at a temperature of 700 ℃ to 900 ℃.
  11. 청구항 8에 있어서,The method according to claim 8,
    상기 단계 2)의 소결은 100℃ 내지 700℃의 온도에서 10시간 이내로 열처리한 것인 것을 특징으로 하는 양극 활물질의 제조방법.The sintering of step 2) is a method of producing a positive electrode active material, characterized in that the heat treatment within 10 hours at a temperature of 100 ℃ to 700 ℃.
  12. 청구항 8에 있어서,The method according to claim 8,
    상기 화학식 1에서 A는 Sr인 것을 특징으로 하는 양극 활물질의 제조방법.In Formula 1, A is a method for producing a positive electrode active material, characterized in that Sr.
  13. 청구항 8에 있어서,The method according to claim 8,
    상기 인산화물 전구체는 (NH4)2HPO4, (NH4)2H2PO4, (NH4)3PO4·(3H2O), H3PO4 및 P2O5으로 이루어진 군으로부터 선택된 1종 이상인 것을 특징으로 하는 양극 활물질의 제조방법.The phosphate precursor is from (NH 4 ) 2 HPO 4 , (NH 4 ) 2 H 2 PO 4 , (NH 4 ) 3 PO 4 · (3H 2 O), H 3 PO 4 and P 2 O 5 Method for producing a positive electrode active material, characterized in that at least one selected.
  14. 제1항 내지 제7항 중 어느 한 항의 양극 활물질을 포함하는 양극 활물질 슬러리가 집전체 상에 도포되어 있는 이차전지용 양극.The positive electrode for secondary batteries in which the positive electrode active material slurry containing the positive electrode active material of any one of Claims 1-7 is apply | coated on an electrical power collector.
  15. 제14항의 이차전지용 양극과 음극, 상기 양극과 음극 사이에 개재된 분리막 및 전해질을 포함하는 리튬 이차전지.A lithium secondary battery comprising a separator and an electrolyte interposed between the positive electrode and the negative electrode of claim 14, the positive electrode and the negative electrode.
  16. 청구항 15에 있어서,The method according to claim 15,
    상기 리튬 이차전지는 45℃에서 1.0 C 충전 및 1.0 C 방전 조건의 55회 사이클(cycle)에서 초기 용량 대비 용량 유지율이 90% 이상인 것을 특징으로 하는 리튬 이차전지.The lithium secondary battery has a capacity retention ratio of 90% or more at initial capacity in 55 cycles of 1.0 C charge and 1.0 C discharge conditions at 45 ° C.
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